enable msbuild server by default for team internal build pipelines

[SimaTian]

Part of #9379

Context

Enable MSBuildServer for our internal pipelines so that we can start troubleshooting any issues that might arise.

Changes Made

Enabled said server by toggling the appropriate environment variables.

Testing

This is the test.

[baronfel]

Just noting that this doesn't use Server for our day to day local builds - I think we want that to increase coverage?

[SimaTian]

Current status:
kills a bunch of tests, mostly related to

• terminal logger
• build checks

[rainersigwald]

Tests should not inherit this environment. Can you unset it with these others? (or maybe "all MSBuild* environment?)

msbuild/src/UnitTests.Shared/TestEnvironment.cs

Lines 56 to 58 in c81c498

	// Clear these two environment variables first in case pre-setting affects the test.
	env.SetEnvironmentVariable("MSBUILDLIVELOGGER", null);
	env.SetEnvironmentVariable("MSBUILDTERMINALLOGGER", null);