RFR: experiment: generate Q descriptors for lw5 code

[Vicente Romero]

This patch allows the generation of Q descriptors for lw5 code. This is just experimental, and the support could be removed at any time without notice

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Commit messages:
 - Update ValueConstructorRef.java
 - Update SideEffectTest.java
 - Update QualifiedSuperCtor.java
 - reusing existing primitive classes tests
 - Merge branch 'lw5' into generate.qdescriptors
 - adding some tests to support Q descriptors experiment
 - additional improvements
 - Merge branch 'lw5' into generate.qdescriptors
 - some refactorings
 - emit Q descriptors, experiments

Changes: https://git.openjdk.org/valhalla/pull/891/files
 Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=891&range=00
  Stats: 1484 lines in 155 files changed: 829 ins; 260 del; 395 mod
  Patch: https://git.openjdk.org/valhalla/pull/891.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/891/head:pull/891

PR: https://git.openjdk.org/valhalla/pull/891