Exception Thrown Rather than Error Message And Help When Command Has Both Custom Parser and Validator

In the code below, running (with SDK 10.0.100-rc.1.25451.107)
```
dotnet run ./TestOne.cs 12 23 34 --dats ab bc cd
```
Leads to an exception being thrown
```
Unhandled exception. System.InvalidOperationException: Argument "--dats" is not two characters long
at System.CommandLine.Binding.ArgumentConverter.GetValueOrDefault[T](ArgumentConversionResult result)
at System.CommandLine.Parsing.ArgumentResult.GetValueOrDefault[T]()
at Program.<>c.<$>b__0_3(ArgumentResult argRes) in [HIDDEN]\TestOne.cs:line 52
at System.CommandLine.Parsing.ArgumentResult.ValidateAndConvert(Boolean useValidators)
at System.CommandLine.Parsing.ArgumentResult.GetArgumentConversionResult()
at System.CommandLine.Parsing.CommandResult.ValidateArgumentsAndAddDefaultResults(Boolean completeValidation)
at System.CommandLine.Parsing.CommandResult.Validate(Boolean isInnermostCommand)
at System.CommandLine.Parsing.ParseOperation.ValidateAndAddDefaultResults()
at System.CommandLine.Parsing.ParseOperation.Parse()
at System.CommandLine.Parsing.CommandLineParser.Parse(Command command, IReadOnlyList`1 arguments, String rawInput, ParserConfiguration configuration)
at System.CommandLine.Parsing.CommandLineParser.Parse(Command command, IReadOnlyList`1 args, ParserConfiguration configuration)
at System.CommandLine.Command.Parse(IReadOnlyList`1 args, ParserConfiguration configuration)
at Program.$(String[] args) in [HIDDEN]\TestOne.cs:line 71
at Program.(String[] args)
```
Rather than the expected, and more helpful:
```
Argument "--dats" is not two characters long

Description:
Test app for System.CommandLine

Usage:
TestOne ... [options]

Arguments:
Root command arguments. One or more pairs of characters separated by space

Options:
--data Option data items
-?, -h, --help Show help and usage information
--version Show version information
```

I noticed this when typo'ing the command line in a rather more complex project.

The problem seems to be that the validator triggers the parser, so there is nothing to check for errors reported by the parser. Without the custom parser the expected error & help is reported.

-----
```csharp
#:package System.CommandLine@2.0.0-rc.1.25451.107
#nullable enable
using System.CommandLine;
using System.CommandLine.Parsing;
using System.Diagnostics;

string[] ParseArguments(ArgumentResult argRes) {
List res = new();
foreach (var a in argRes.Tokens) {
var s = a.Value;
if (s.Length != 2) {
argRes.AddError($"Argument \"{s}\" is not two characters long");
} else {
res.Add(s);
}
}
return res.ToArray();
}

void ValidateArguments(string[] rawValues, Action reportError) {
if (rawValues.Length == 0) {
reportError("No arguments provided");
return;
}

foreach (var rawValue in rawValues) {
if (rawValue.Length != 2) {
reportError($"Argument \"{rawValue}\" is not two characters long");
} else if (rawValue[0] >= rawValue[1]) {
reportError($"In argument \"{rawValue}\" the first letter does not precede, in Unicode code point order, the second");
}
}
}

var dataOption = new Option("--data") {
Description = "Option data items",
Arity = ArgumentArity.OneOrMore,
Required = false,
AllowMultipleArgumentsPerToken = true
};
dataOption.Validators.Add(optRes => {
var args = optRes.GetValueOrDefault();
ValidateArguments(args, msg => optRes.AddError(msg));
});

var rootCmdArgs = new Argument("TestOne") {
Description = "Root command arguments. One or more pairs of characters separated by space",
Arity = ArgumentArity.OneOrMore
};
rootCmdArgs.CustomParser = ParseArguments;
rootCmdArgs.Validators.Add(argRes => {
var args = argRes.GetValueOrDefault();
ValidateArguments(args, msg => argRes.AddError(msg));
});

var rootCmd = new RootCommand("Test app for System.CommandLine") {
dataOption,
rootCmdArgs
};
rootCmd.SetAction(parseResult => {
var args = parseResult.GetValue(rootCmdArgs);
var dataArgs = parseResult.GetValue(dataOption);
Debug.Assert(args is not null);
Debug.Assert(dataArgs is not null);
Console.WriteLine("Root command");
Console.WriteLine($" args: {String.Join(", ", args.Select(a => $"\"{a}\""))}");
Console.WriteLine($" data: {String.Join(", ", dataArgs.Select(a => $"\"{a}\""))}");
});

var parse = rootCmd.Parse(args);
await parse.InvokeAsync();
```