Add --ansi option to force Ansi output

[powercode]

Summary

Add the complement to --no-ansi, that forces --ansi output, even if output is redirected.

Background and Motivation

When running the tests from a PowerShell script, I may want to display the test output but not have it as output from the PowerShell function.

mytest.exe | Out-Host
if ($LASTEXITCODE){
   throw "test failed"
}

This removes all coloring from the output, even though it's logically equivalent to passing it directly to the terminal for display.

Proposed Feature

Add --ansi parameter that forces ansi output, regardless of redirection. Let the user decide.

Alternative Designs

Always output ansi unless the user explicitly uses --no-ansi.
That has the drawback of potentially breaking existing scripts.

[Evangelink]

It's probably a quick and easy update so I don't see why not! Thanks for the suggestion @powercode.

cc @mariam-abdulla as it might require some porting to dotnet test.