[vectorIntrinsics+compress] RFR: 8274889: Intrinsify Vector.expand/compress APIs for X86 [v4]

[Jatin Bhateja]

> - Common C2 compiler entry point for compress/expand APIs.
> - Inline expansion handling and C2 graph creation.
> - For X86 current backed support is added for AVX512 which offers direct compress/expand instructions.

Jatin Bhateja has updated the pull request incrementally with two additional commits since the last revision:

 - 8274889: Backing out generic handling for background vectors in compression/expansion operation.
 - 8274889: Review comments resolved.

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Changes:
  - all: https://git.openjdk.java.net/panama-vector/pull/146/files
  - new: https://git.openjdk.java.net/panama-vector/pull/146/files/0d1e7c32..c899a604

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=panama-vector&pr=146&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=panama-vector&pr=146&range=02-03

  Stats: 137 lines in 17 files changed: 3 ins; 20 del; 114 mod
  Patch: https://git.openjdk.java.net/panama-vector/pull/146.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-vector pull/146/head:pull/146

PR: https://git.openjdk.java.net/panama-vector/pull/146