[lworld+fp16] RFR: Merge lworld [v2]

[Jatin Bhateja]

> Merge latest lworld code into lworld+fp16.
> 
> All existing Float16 tests are passing post merge.
> 
> Best Regards,
> Jatin

Jatin Bhateja has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 13 commits:

 - Merge branch 'lworld' of http://github.com/openjdk/valhalla into merge_lworld2fp16
 - 8334432: Refine Float16.fma
   
   Co-authored-by: Raffaello Giulietti <rgiulietti at openjdk.org>
   Reviewed-by: jbhateja, rgiulietti
 - 8337605: Update description of constants in Float16
   
   Reviewed-by: bkilambi, rgiulietti, jbhateja
 - 8338102: x86 backend support for newly added Float16 intrinsics.
   
   Reviewed-by: bkilambi
 - 8336406: Add support for FP16 binary operations
   
   Reviewed-by: jbhateja
 - 8330021: AArch64: Add backend support for FP16 add operation
   
   Reviewed-by: jbhateja
 - 8333852: Allow flat array layout for value based classes.
   
   Reviewed-by: bkilambi
 - 8329817: Augment prototype Float16 class
   
   Reviewed-by: jbhateja
 - Merge lworld
 - Merge lworld
 - ... and 3 more: https://git.openjdk.org/valhalla/compare/e19d6796...ca179277

-------------

Changes: https://git.openjdk.org/valhalla/pull/1213/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=1213&range=01
  Stats: 5503 lines in 74 files changed: 4700 ins; 4 del; 799 mod
  Patch: https://git.openjdk.org/valhalla/pull/1213.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/1213/head:pull/1213

PR: https://git.openjdk.org/valhalla/pull/1213