[WIP] Print clear informational message when launchSettings.json is used by dotnet test

[Copilot]

Thanks for assigning this issue to me. I'm starting to work on it and will keep this PR's description up to date as I form a plan and make progress.

Original issue description:

If we picked up launchSettings.json, we should clearly print that we did, and show the path to it. We should make this similar to dotnet run:

sdk/src/Cli/dotnet/Commands/Run/RunCommand.cs

Lines 211 to 214 in 248fbc7

	if (MSBuildArgs.Verbosity?.IsQuiet() != true)
	{
	Reporter.Output.WriteLine(string.Format(CliCommandStrings.UsingLaunchSettingsFromMessage, launchSettingsPath));
	}

We already have tests for launchSettings in GivenDotnetTestBuildsAndRunsTests

Fixes #49713.

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