Policy/procedures for replacement of azure test/build pipelines

[ghazen-ml]

Now that Azure pipeline is no longer running, it would be great to decide a policy/procedure for running tests and producing release npms. Either using a github pipeline or a policy of maintainers running tests before approving, etc.

This script can run all tests locally
https://github.com/MixedRealityToolkit/MixedRealityToolkit-Unity/blob/main/Tooling/Test/run_playmode_tests.ps1