RFR: 8330844: Add aliases for conditional jumps and additional instruction forms for x86 [v3]

[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:

  Revert changes to 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/0b95b3af..f7d7f7de

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=18893&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=18893&range=01-02

  Stats: 90 lines in 2 files changed: 0 ins; 67 del; 23 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