[dsrouter] log redirected console output

[jonathanpeppers]

Context: #5494
Context: #5241
Fixes: #5435

We added --dsrouter switch to both dotnet-trace and dotnet-gcdump, which runs dotnet-dsrouter as a child process.

Many of dotnet-dsrouter's console messages are pretty useful for developers, but we are simply ignoring them:

private static async Task ReadAndIgnoreAllStreamAsync(StreamReader streamToIgnore, CancellationToken cancelToken)
{
    Memory<char> memory = new char[4096];
    while (await streamToIgnore.ReadAsync(memory, cancelToken).ConfigureAwait(false) != 0)
    {
    }
}

To make this a bit more useful, we now log the output to either Console.Out or Console.Error where appropriate.

If we simply did:

string line;
while ((line = await streamToRead.ReadLineAsync(cancelToken).ConfigureAwait(false)) != null)
{
    output.WriteLine(line);
}

This would work fine, but we'd lose all coloring.

dotnet-dsrouter uses SimpleConsoleFormatter to colorize its output:

https://github.com/dotnet/runtime/blob/aadcceeb03ce0ecbc2ad645de0feb10189daa64c/src/libraries/Microsoft.Extensions.Logging.Console/src/SimpleConsoleFormatter.cs#L163-L199

So, for now, a very simple solution is to check the known prefixes and add coloring. This looks to have a pretty good result.

I also dropped the duplicate message:

WARNING: dotnet-dsrouter is a development tool not intended for production environments.

Now that we print all of dotnet-dsrouter's output, we can handle this case and color it yellow.

[tommcdon]

LGTM, thank you!

[lateralusX]

@jonathanpeppers Did you test how this works with dotnet-trace? Since it uses the console differently to track progress, having log messages added to the console once it starts to collect might have side effects on the progress logging. Did you have a look on how it behaves?

[jonathanpeppers]

@lateralusX I think dotnet-trace is working ok: