[lworld+fp16] Integrated: Merge lworld

[Jatin Bhateja]

Summary of changes:-

Merge latest lworld into lworld+fp16.
Make Float16 a ValueBased and ImplicitlyConstructible class. It encapsulates a 'short' field to hold an IEEE 754 binary16 encoded value.
Facilitate a flat array layout for array allocations whose elements type is an implicitly constructible value class.

Best Regards,
Jatin

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Commit messages:
 - Merge branch 'lworld' of http://github.com/openjdk/valhalla into merge_lworld_into_fp16
 - Merge lworld
 - [lworld+fp16] Merge lworld
 - 8308363: Initial compiler support for FP16 scalar operations.
 - Merge lworld

The merge commit only contains trivial merges, so no merge-specific webrevs have been generated.

Changes: https://git.openjdk.org/valhalla/pull/1120/files
  Stats: 1592 lines in 42 files changed: 1553 ins; 3 del; 36 mod
  Patch: https://git.openjdk.org/valhalla/pull/1120.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1120/head:pull/1120

PR: https://git.openjdk.org/valhalla/pull/1120