Too many open files on my solution

## Issue Description ##
Unable to work normally with my solution because of "Too many open files". inotify watches is set to maximum:
```
cat /proc/sys/fs/inotify/max_user_watches
524288
```
In the folder I've opened lays several dotnet solutions, biggest one with 300+ projects.
## Steps to Reproduce ##
Open folder with solution.
Wait for 3-5 minutes.
## Expected Behavior ##
VSCode able to work with big solution
## Actual Behavior ##
VSCode unable to work with big solution

### OmniSharp log ###
```
System.InvalidOperationException: object_op ---> System.IO.IOException: Too many open files
at System.IO.Enumeration.FileSystemEnumerator`1[TResult].CreateDirectoryHandle (System.String path, System.Boolean ignoreNotFound) [0x00032] in <4f52a2659e1844fea7ab38854dcbcf68>:0
at System.IO.Enumeration.FileSystemEnumerator`1[TResult]..ctor (System.String directory, System.IO.EnumerationOptions options) [0x00048] in <4f52a2659e1844fea7ab38854dcbcf68>:0
at System.IO.Enumeration.FileSystemEnumerable`1+DelegateEnumerator[TResult]..ctor (System.IO.Enumeration.FileSystemEnumerable`1[TResult] enumerable) [0x00000] in <4f52a2659e1844fea7ab38854dcbcf68>:0
at System.IO.Enumeration.FileSystemEnumerable`1[TResult]..ctor (System.String directory, System.IO.Enumeration.FileSystemEnumerable`1+FindTransform[TResult] transform, System.IO.EnumerationOptions options) [0x00042] in <4f52a2659e1844fea7ab38854dcbcf68>:0
at System.IO.Enumeration.FileSystemEnumerableFactory.UserDirectories (System.String directory, System.String expression, System.IO.EnumerationOptions options) [0x00014] in <4f52a2659e1844fea7ab38854dcbcf68>:0
at System.IO.Directory.InternalEnumeratePaths (System.String path, System.String searchPattern, System.IO.SearchTarget searchTarget, System.IO.EnumerationOptions options) [0x00045] in <4f52a2659e1844fea7ab38854dcbcf68>:0
at System.IO.Directory.EnumerateDirectories (System.String path, System.String searchPattern, System.IO.EnumerationOptions enumerationOptions) [0x00000] in <4f52a2659e1844fea7ab38854dcbcf68>:0
at System.IO.Directory.EnumerateDirectories (System.String path) [0x0000b] in <4f52a2659e1844fea7ab38854dcbcf68>:0
at System.IO.CoreFX.FileSystemWatcher+RunningInstance.AddDirectoryWatchUnlocked (System.IO.CoreFX.FileSystemWatcher+RunningInstance+WatchedDirectory parent, System.String directoryName) [0x0016c] in <883cd000faa842148a99b174e3bd5ca4>:0
at System.IO.CoreFX.FileSystemWatcher+RunningInstance.AddDirectoryWatchUnlocked (System.IO.CoreFX.FileSystemWatcher+RunningInstance+WatchedDirectory parent, System.String directoryName) [0x0018d] in <883cd000faa842148a99b174e3bd5ca4>:0
at System.IO.CoreFX.FileSystemWatcher+RunningInstance.AddDirectoryWatchUnlocked (System.IO.CoreFX.FileSystemWatcher+RunningInstance+WatchedDirectory parent, System.String directoryName) [0x0018d] in <883cd000faa842148a99b174e3bd5ca4>:0
at System.IO.CoreFX.FileSystemWatcher+RunningInstance.AddDirectoryWatchUnlocked (System.IO.CoreFX.FileSystemWatcher+RunningInstance+WatchedDirectory parent, System.String directoryName) [0x0018d] in <883cd000faa842148a99b174e3bd5ca4>:0
at System.IO.CoreFX.FileSystemWatcher+RunningInstance.AddDirectoryWatchUnlocked (System.IO.CoreFX.FileSystemWatcher+RunningInstance+WatchedDirectory parent, System.String directoryName) [0x0018d] in <883cd000faa842148a99b174e3bd5ca4>:0
at System.IO.CoreFX.FileSystemWatcher+RunningInstance.AddDirectoryWatchUnlocked (System.IO.CoreFX.FileSystemWatcher+RunningInstance+WatchedDirectory parent, System.String directoryName) [0x0018d] in <883cd000faa842148a99b174e3bd5ca4>:0
at System.IO.CoreFX.FileSystemWatcher+RunningInstance.AddDirectoryWatchUnlocked (System.IO.CoreFX.FileSystemWatcher+RunningInstance+WatchedDirectory parent, System.String directoryName) [0x0018d] in <883cd000faa842148a99b174e3bd5ca4>:0
at System.IO.CoreFX.FileSystemWatcher+RunningInstance.AddDirectoryWatchUnlocked (System.IO.CoreFX.FileSystemWatcher+RunningInstance+WatchedDirectory parent, System.String directoryName) [0x0018d] in <883cd000faa842148a99b174e3bd5ca4>:0
at System.IO.CoreFX.FileSystemWatcher+RunningInstance.AddDirectoryWatchUnlocked (System.IO.CoreFX.FileSystemWatcher+RunningInstance+WatchedDirectory parent, System.String directoryName) [0x0018d] in <883cd000faa842148a99b174e3bd5ca4>:0
at System.IO.CoreFX.FileSystemWatcher+RunningInstance..ctor (System.IO.CoreFX.FileSystemWatcher watcher, Microsoft.Win32.SafeHandles.SafeFileHandle inotifyHandle, System.String directoryPath, System.Boolean includeSubdirectories, System.IO.NotifyFilters notifyFilters, System.Threading.CancellationToken cancellationToken) [0x0005c] in <883cd000faa842148a99b174e3bd5ca4>:0
at System.IO.CoreFX.FileSystemWatcher.StartRaisingEvents () [0x000dd] in <883cd000faa842148a99b174e3bd5ca4>:0
at System.IO.CoreFX.FileSystemWatcher.StartRaisingEventsIfNotDisposed () [0x00019] in <883cd000faa842148a99b174e3bd5ca4>:0
at System.IO.CoreFX.FileSystemWatcher.set_EnableRaisingEvents (System.Boolean value) [0x0001d] in <883cd000faa842148a99b174e3bd5ca4>:0
at (wrapper remoting-invoke-with-check) System.IO.CoreFX.FileSystemWatcher.set_EnableRaisingEvents(bool)
at System.IO.CoreFXFileSystemWatcherProxy+<>c.b__9_0 (System.IO.CoreFX.FileSystemWatcher internal_fsw, System.IO.FileSystemWatcher fsw) [0x00048] in <883cd000faa842148a99b174e3bd5ca4>:0
at System.IO.CoreFXFileSystemWatcherProxy.Operation (System.Action`4[T1,T2,T3,T4] map_op, System.Action`2[T1,T2] object_op, System.Object handle, System.Action`2[T1,T2] cancel_op) [0x00184] in <883cd000faa842148a99b174e3bd5ca4>:0
--- End of inner exception stack trace ---
at System.IO.CoreFXFileSystemWatcherProxy.Operation (System.Action`4[T1,T2,T3,T4] map_op, System.Action`2[T1,T2] object_op, System.Object handle, System.Action`2[T1,T2] cancel_op) [0x001a6] in <883cd000faa842148a99b174e3bd5ca4>:0
at System.IO.CoreFXFileSystemWatcherProxy.StartDispatching (System.Object handle) [0x00004] in <883cd000faa842148a99b174e3bd5ca4>:0
at System.IO.FileSystemWatcher.Start () [0x0001b] in <883cd000faa842148a99b174e3bd5ca4>:0
at System.IO.FileSystemWatcher.set_EnableRaisingEvents (System.Boolean value) [0x0003d] in <883cd000faa842148a99b174e3bd5ca4>:0
at (wrapper remoting-invoke-with-check) System.IO.FileSystemWatcher.set_EnableRaisingEvents(bool)
at Microsoft.AspNetCore.Razor.OmniSharpPlugin.MSBuildProjectDocumentChangeDetector.ProjectLoaded (OmniSharp.MSBuild.Notification.ProjectLoadedEventArgs loadedArgs) [0x00266] in <8c6f4eb2e16d4051ba80a599aba81c54>:0
at OmniSharp.MSBuild.ProjectManager.ProcessQueue (System.Threading.CancellationToken cancellationToken) [0x00198] in <559e0651ed234d568cb45fca36d98a0c>:0
```
## Environment information ##

**VSCode version**: 1.39.2
**C# Extension**: 1.21.5

Mono Information
OmniSharp using global mono :6.0.0
Dotnet Information
.NET Core SDK (reflecting any global.json):
Version: 2.2.108
Commit: 33ed5b90ce

Runtime Environment:
OS Name: arch
OS Version:
OS Platform: Linux
RID: arch-x64
Base Path: /opt/dotnet/sdk/2.2.108/

Host (useful for support):
Version: 2.2.6
Commit: 7dac9b1b51

.NET Core SDKs installed:
2.2.108 [/opt/dotnet/sdk]

.NET Core runtimes installed:
Microsoft.NETCore.App 2.2.6 [/opt/dotnet/shared/Microsoft.NETCore.App]

To install additional .NET Core runtimes or SDKs:
https://aka.ms/dotnet-download

Visual Studio Code Extensions

|Extension|Author|Version|
|---|---|---|
|csharp|ms-vscode|1.21.5|
|dotenv|mikestead|1.0.1|
|EditorConfig|EditorConfig|0.14.2|
|Go|ms-vscode|0.11.7|
|Material-theme|zhuangtongfa|2.28.2|
|path-intellisense|christian-kohler|1.4.2|
|plantuml|jebbs|2.12.1|
|rainbow-csv|mechatroner|1.3.1|
|rest-client|humao|0.22.2|
|synthwave-vscode|RobbOwen|0.0.7|
|terraform|mauve|1.4.0|
|vscode-docker|ms-azuretools|0.8.1|
|vscode-icons|vscode-icons-team|9.5.0|
|vscode-yaml|redhat|0.5.3|;