[jdk21u-dev] RFR: 8307352: AARCH64: Improve itable_stub

[Dmitry Chuyko]

This is a clean backport of itable_stub optimization for aarch64. x86 part was made in JDK 21, aarch64 landed only in JDK 22. There is JDK-8323122 (increase stub estimate) from JDK 23 as a safety follow-up (not mandatory).

Testing: tier1,2 on linux-aarch64. Benchmark result on jdk21-dev match the original improvement numbers.

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Commit messages:
 - Backport c664f1ca660adea934f099de8595b6ec10d3a824

Changes: https://git.openjdk.org/jdk21u-dev/pull/683/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=683&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8307352
  Stats: 133 lines in 4 files changed: 113 ins; 15 del; 5 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/683.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/683/head:pull/683

PR: https://git.openjdk.org/jdk21u-dev/pull/683