Set some environment variables for more verbose logging during recording

[KirillOsenkov]

When the extension is in "recording" mode it should set a few environment variables to make logging more verbose. Here's an example where BinaryLogger sets these:

https://github.com/Microsoft/msbuild/blob/715c0a55d7d447e1fa84f54b6985bd458f226cd3/src/Build/Logging/BinaryLogger/BinaryLogger.cs#L91

We probably need to set them early enough before node processes are created so that they can inherit the values.

Here's where this environment variable is consumed:
https://source.dot.net/#Microsoft.Build/Evaluation/Evaluator.cs,7d58222c828c5f83,references