v2.0.0-M0 for scalac and compiler plugins

[ghost]

M0 version, no scala-js but should be OK to build scalac and some compiler plugins.

[gslowikowski]

Read scoverage/scalac-scoverage-plugin-core#1 (comment) first.

Additional notes:

• plugin and runtime modules should be fixed here, not moved to separate repo to avoid git history loss
• reporting module shouldn't depend on scala-compiler

[ckipp01]

Seeing that this is from 5 years ago, I'm going to go ahead and close. We can revisit if need be, but I think for the time being there are other things to look at before considering a massive change like this.