[lworld] RFR: 8315412 [lworld] Preparing code for lw5

[Frederic Parain]

Quite a big patch, but it is mostly made of renaming and mechanical replacement without really changing the logic of the code.

The patch includes changes to make the VM code less dependent on Q-descriptors by encoding the presence of null-free inline types fields in FieldInfo.

The patch also includes a lot of renaming, in an effort to have uniformed naming of flat fields and flat arrays across the VM. The renaming has not been applied to the heap dumper and C2. They will be addressed in follow up patches.

Tested with Mach5, tiers 1 to 3.

Thank you

Fred

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Commit messages:
 - Merge remote-tracking branch 'upstream/lworld' into qdesc_removal
 - Renaming and preparation for q-descriptors removal

Changes: https://git.openjdk.org/valhalla/pull/922/files
 Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=922&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8315412
  Stats: 689 lines in 79 files changed: 99 ins; 88 del; 502 mod
  Patch: https://git.openjdk.org/valhalla/pull/922.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/922/head:pull/922

PR: https://git.openjdk.org/valhalla/pull/922