JBIDE-11766 - Work with "Annotation Properties" view breaks JAX-RS explorer

- Using jobs to process Java changes and Resource changes, with a scheduling rule
to avoid concurrency (race conditions).
- Fixing unit tests that now need to wait until the jobs (running asynchronously in another thread)
are done before doing the assertions, with a timeout (set to a lage enough value to allow for debugging)
- Fixed usage of compilation unit's working copy vs primary copy in some tests.
- Calling "ICompilationUnit.makeConsistent(IProgressMonitor)" resolves the problem where in some
  cases, some JAX-RS annotations would not be "seen" by the JAX-RS tooling, resulting in elements being removed
- Removed the CompilationUnitRepository which worked as a cache for the Compilation Units AST, but could contain stale data
- Changed the 'Refresh Action' to trigger a real metamodel build ad then refresh the UI, which avoids the need to perform a project build.
JBIDE-18453 - NPE while processing change in code

Remove a block where the signature of the Java methods were collected but not used
(a remaining of a previous refactoring)
Added some 'waits' in the unit tests (with a bit of API refactoring in the test utility classes) because
some tests would fail with ConcurrentModificationException on maven (some elements would still be processed
in a separate thread when doing the test assertions)