sbt 2.x Port

[anatoliykmetyuk]

This PR implements a cross-build of the plugin to sbt 2.

Status

Core sbt 2.x port is done.
CI is red due to test setup issues (details below).

What works

• Plugin logic is fully ported to sbt 2 APIs
• Unit tests pass

What’s missing

Scripted tests fail due to the library paths being hard-coded in the checks. For example, in auto/build.sbt:

  if (updates.keySet != Set(ModuleID("org.scala-lang", "scala-library", "2.10.4")))
    sys.error(s"Wrong update keys: ${updates.keySet}")

[info] [error] java.lang.RuntimeException: Wrong update keys: Set(org.scala-lang:scala-library:2.10.4)