Exclusive context policy ensures EnsoContext.get returns compilation constant

[JaroslavTulach]

Pull Request Description

Fixes #6809 by giving up on any attempt to share Node among multiple Context via sharing a single Engine.

Checklist

Please ensure that the following checklist has been satisfied before submitting the PR:

• All code follows the
  Java,
• All code has been tested:
  • Another benchmark results are sane
  • Final benchmark results are OK
  • SharedContextTest is passing

[JaroslavTulach]

There is a discussion about ContextReference at GraalVM slack. Technically ContextReference shall return a compilation constant, but it didn't so far. Using EXCLUSIVE context policy turn EnsoContext.get into compilation constant - that might also speed up our benchmarks.

[Akirathan]

This is very cool. Not only the performance might be better, but also some asserts should stop failing.

[JaroslavTulach]

This is a test taken from branch wip/jtulach/NoTypeInNodePlease_6809. The test seems to pass OK with EXCLUSIVE context policy.

[JaroslavTulach]

SharedEngineTest fails on the CI trying to download an edition. Probably an Engine configuration problem.

[JaroslavTulach]

DebuggingEnsoTest asserts - fixed in d1b5913

[JaroslavTulach]

The first Benchmark results were not good, but the second benchmark results are sane. Running 3rd benchmark results to confirm the result.

I think the results are OK and we can integrate.