RFR: 8330844: Add aliases for conditional jumps and additional instruction forms for x86

[Scott Gibbons]

Adding infrastructure for JDK-8320448.  Aliasing conditional jump instructions; making arrays_equals accessible from stubs; adding some x86 instructions.

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Commit messages:
 - Add conditional jump aliases; move arrays_equals; add instructions

Changes: https://git.openjdk.org/jdk/pull/18893/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18893&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8330844
  Stats: 654 lines in 6 files changed: 439 ins; 215 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/18893.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18893/head:pull/18893

PR: https://git.openjdk.org/jdk/pull/18893