RFR: 8372617: Save and restore stubgen stubs when using an AOT code cache [v2]

[Andrew Dinn]

> This PR adds save and restore of all generated stubs to the AOT code cache on x86 and aarch64. Other arches are modified to deal with the related generic PAI changes.
> 
> Small changes were required to the aarch64 and x86_64 generator code in order to meet two key constraints:
> 1. the first declared entry of every stub starts at the first instruction in the stub code range
> 2. all data/code cross-references from one stub to another target a declared stub entry

Andrew Dinn has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 33 commits:

 - fix AOT externals after merge with main branch
 - Merge branch 'master' into save-stubgen-stubs
 - fix header declarations
 - move AOT address init impl into arch tree below StubRoutines
 - put AOT address table init code under INCLUDE_CDS
 - fix extras count to match number of unsafe handler regions
 - merge
 - more whitespace
 - rmeove whitespace
 - remove redundant comment
 - ... and 23 more: https://git.openjdk.org/jdk/compare/e0edc656...6e221ac6

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Changes: https://git.openjdk.org/jdk/pull/28433/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28433&range=01
  Stats: 5388 lines in 59 files changed: 4467 ins; 443 del; 478 mod
  Patch: https://git.openjdk.org/jdk/pull/28433.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28433/head:pull/28433

PR: https://git.openjdk.org/jdk/pull/28433