Connection gets stuck in SNITCPHandle.TryConnectParallel

### Describe the bug
SqlConnection.Open gets stuck in SNITCPHandle.TryConnectParallel and times out when there is no available threads in thread pool.

Exception message:
```
Microsoft.Data.SqlClient.SqlException (0x80131904): A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: TCP Provider, error: 40 - Could not open a connection to SQL Server: Could not open a connection to SQL Server)
```
Stack trace:
```
at Microsoft.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction)
at Microsoft.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose)
at Microsoft.Data.SqlClient.TdsParser.Connect(ServerInfo serverInfo, SqlInternalConnectionTds connHandler, Boolean ignoreSniOpenTimeout, Int64 timerExpire, SqlConnectionString connectionOptions, Boolean withFailover)
at Microsoft.Data.SqlClient.SqlInternalConnectionTds.AttemptOneLogin(ServerInfo serverInfo, String newPassword, SecureString newSecurePassword, Boolean ignoreSniOpenTimeout, TimeoutTimer timeout, Boolean withFailover)
at Microsoft.Data.SqlClient.SqlInternalConnectionTds.LoginNoFailover(ServerInfo serverInfo, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance, SqlConnectionString connectionOptions, SqlCredential credential, TimeoutTimer timeout)
at Microsoft.Data.SqlClient.SqlInternalConnectionTds.OpenLoginEnlist(TimeoutTimer timeout, SqlConnectionString connectionOptions, SqlCredential credential, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance)
at Microsoft.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, SqlCredential credential, Object providerInfo, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance, SqlConnectionString userConnectionOptions, SessionData reconnectSessionData, Boolean applyTransientFaultHandling, String accessToken, DbConnectionPool pool)
at Microsoft.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, DbConnectionPoolKey poolKey, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection, DbConnectionOptions userOptions)
at Microsoft.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnectionPool pool, DbConnection owningObject, DbConnectionOptions options, DbConnectionPoolKey poolKey, DbConnectionOptions userOptions)
at Microsoft.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection)
at Microsoft.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection)
at Microsoft.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32 waitForMultipleObjectsTimeout, Boolean allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions userOptions, DbConnectionInternal& connection)
at Microsoft.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal& connection)
at Microsoft.Data.ProviderBase.DbConnectionFactory.TryGetConnection(DbConnection owningConnection, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal oldConnection, DbConnectionInternal& connection)
at Microsoft.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)
at Microsoft.Data.ProviderBase.DbConnectionClosed.TryOpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)
at Microsoft.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource`1 retry, SqlConnectionOverrides overrides)
at Microsoft.Data.SqlClient.SqlConnection.Open(SqlConnectionOverrides overrides)
at Microsoft.Data.SqlClient.SqlConnection.Open()
```

We have an ASP.NET HTTP application running in Alpine Linux in K8S. The application makes synchronous SQL requests to the database. During the peak load we sometimes experience a cascade of connection failures.

Dump files collected during the incident contain a number of threads waiting in SNITCPHandle.TryConnectParallel. This method uses sync-over-async to connect to multiple IP addresses in parallel. This, coupled with the thread pool exhaustion caused by a big amount of incoming requests, may be the reason for timeouts.

Stack trace from the dump file:
```
System.Threading.ManualResetEventSlim.Wait(Int32, System.Threading.CancellationToken)
System.Threading.Tasks.Task.SpinThenBlockingWait(Int32, System.Threading.CancellationToken)
System.Threading.Tasks.Task.InternalWaitCore(Int32, System.Threading.CancellationToken)
System.Threading.Tasks.Task.Wait(Int32, System.Threading.CancellationToken)
System.Threading.Tasks.Task.Wait(System.TimeSpan)
Microsoft.Data.SqlClient.SNI.SNITCPHandle.TryConnectParallel(System.String, Int32, System.TimeSpan, Boolean, Boolean ByRef, System.String, Microsoft.Data.SqlClient.SQLDNSInfo ByRef)
Microsoft.Data.SqlClient.SNI.SNITCPHandle..ctor(System.String, Int32, Int64, Boolean, Microsoft.Data.SqlClient.SqlConnectionIPAddressPreference, System.String, Microsoft.Data.SqlClient.SQLDNSInfo ByRef)
Microsoft.Data.SqlClient.SNI.SNIProxy.CreateTcpHandle(Microsoft.Data.SqlClient.SNI.DataSource, Int64, Boolean, Microsoft.Data.SqlClient.SqlConnectionIPAddressPreference, System.String, Microsoft.Data.SqlClient.SQLDNSInfo ByRef)
Microsoft.Data.SqlClient.SNI.SNIProxy.CreateConnectionHandle(System.String, Boolean, Int64, Byte[] ByRef, Byte[][] ByRef, Boolean, Boolean, Boolean, Boolean, Microsoft.Data.SqlClient.SqlConnectionIPAddressPreference, System.String, Microsoft.Data.SqlClient.SQLDNSInfo ByRef)
Microsoft.Data.SqlClient.SNI.TdsParserStateObjectManaged.CreatePhysicalSNIHandle(System.String, Boolean, Int64, Byte[] ByRef, Byte[][] ByRef, Boolean, Boolean, Boolean, Microsoft.Data.SqlClient.SqlConnectionIPAddressPreference, System.String, Microsoft.Data.SqlClient.SQLDNSInfo ByRef, Boolean)
Microsoft.Data.SqlClient.TdsParser.Connect(Microsoft.Data.SqlClient.ServerInfo, Microsoft.Data.SqlClient.SqlInternalConnectionTds, Boolean, Int64, Boolean, Boolean, Boolean, Boolean, Microsoft.Data.SqlClient.SqlAuthenticationMethod)
Microsoft.Data.SqlClient.SqlInternalConnectionTds.AttemptOneLogin(Microsoft.Data.SqlClient.ServerInfo, System.String, System.Security.SecureString, Boolean, Microsoft.Data.ProviderBase.TimeoutTimer, Boolean)
Microsoft.Data.SqlClient.SqlInternalConnectionTds.LoginNoFailover(Microsoft.Data.SqlClient.ServerInfo, System.String, System.Security.SecureString, Boolean, Microsoft.Data.SqlClient.SqlConnectionString, Microsoft.Data.SqlClient.SqlCredential, Microsoft.Data.ProviderBase.TimeoutTimer)
Microsoft.Data.SqlClient.SqlInternalConnectionTds.OpenLoginEnlist(Microsoft.Data.ProviderBase.TimeoutTimer, Microsoft.Data.SqlClient.SqlConnectionString, Microsoft.Data.SqlClient.SqlCredential, System.String, System.Security.SecureString, Boolean)
Microsoft.Data.SqlClient.SqlInternalConnectionTds..ctor(Microsoft.Data.ProviderBase.DbConnectionPoolIdentity, Microsoft.Data.SqlClient.SqlConnectionString, Microsoft.Data.SqlClient.SqlCredential, System.Object, System.String, System.Security.SecureString, Boolean, Microsoft.Data.SqlClient.SqlConnectionString, Microsoft.Data.SqlClient.SessionData, Boolean, System.String, Microsoft.Data.ProviderBase.DbConnectionPool)
Microsoft.Data.SqlClient.SqlConnectionFactory.CreateConnection(Microsoft.Data.Common.DbConnectionOptions, Microsoft.Data.Common.DbConnectionPoolKey, System.Object, Microsoft.Data.ProviderBase.DbConnectionPool, System.Data.Common.DbConnection, Microsoft.Data.Common.DbConnectionOptions)
Microsoft.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(Microsoft.Data.ProviderBase.DbConnectionPool, System.Data.Common.DbConnection, Microsoft.Data.Common.DbConnectionOptions, Microsoft.Data.Common.DbConnectionPoolKey, Microsoft.Data.Common.DbConnectionOptions)
```

### To reproduce

The following code reproduces the issue in Ubuntu 22.04 running in WSL. MultiSubnetFailover=True switches SNITCPHandle to use TryConnectParallel and triggers the bug.

```c#
using Microsoft.Data.SqlClient;

// Create thread pool exhaustion condition
List tasks = new();
for (int i = 0; i < 10000; ++i)
tasks.Add(Waiter());

Console.WriteLine("Press any key to execute query, press q to quit...");
// Run synchronous query
while (Console.ReadKey().KeyChar != 'q')
Console.WriteLine(Version());

async Task Waiter()
{
await Task.Delay(100);
Task.Delay(Timeout.Infinite).Wait();
}

string Version()
{
using var conn = new SqlConnection("Server=tcp:127.0.0.1,1433;User ID=sa;Password=Password1;Trust server certificate=True;MultiSubnetFailover=True");
conn.Open();
var cmd = conn.CreateCommand();
cmd.CommandText = "SELECT @@VERSION AS Version";
var r = cmd.ExecuteReader();
if (r.Read())
{
return (string)r["Version"];
}
return string.Empty;
}
```

### Expected behavior
Synchronous SqlConnection.Open should be able to connect to SQL server regardless of the current ThreadPool usage.

### Further technical details
Microsoft.Data.SqlClient version: 5.1.1
.NET target: .NET6
SQL Server version: SQL Server 2022
Operating system: Alpine 3.18 in a Docker container

**Additional context**
SQL server for the repro case was installed in Docker using the following command
```
docker run -e "ACCEPT_EULA=Y" -e "MSSQL_SA_PASSWORD=Password1" -p 1433:1433 -d mcr.microsoft.com/mssql/server:2022-latest
```