RFR: 8330844: Add aliases for conditional jumps and additional instruction forms for x86 [v2]

[Scott Gibbons]

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

Scott Gibbons has updated the pull request incrementally with one additional commit since the last revision:

  Undo move of arrays_equals

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Changes:
  - all: https://git.openjdk.org/jdk/pull/18893/files
  - new: https://git.openjdk.org/jdk/pull/18893/files/74d47302..0b95b3af

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=18893&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=18893&range=00-01

  Stats: 564 lines in 4 files changed: 282 ins; 282 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