.NET test output has no colors

Currently the ".NET Test Log" output window drops the colorization from the underlying test runner.


Test runs in the terminal show that there are some useful colors which make it easier to scan the test output:


Going by microsoft/vscode#571 it seems like OutputChannel (the API powering the .NET Test Log) does not support colours in output and is unlikely to anytime soon.

Perhaps nicely colourized test output could instead be achieved by moving the .NET Test Log to use the [createTerminal(options: ExtensionTerminalOptions)](https://code.visualstudio.com/api/references/vscode-api#window.createTerminal) API instead, using a pseudoterminal controlled by the extension.