RFR: 8366477: Refactor AOT-related flag bits in klass.hpp [v3]

[Ioi Lam]

> This PR is one (of many) steps in [JDK-8366473](https://bugs.openjdk.org/browse/JDK-8366473) (Refactor CDS source code with new AOT terminology):
> 
> 1. Rename from `Klass::_shared_class_flags` to `Klass::_aot_class_flags`
> 2. Move `_has_aot_safe_initializer` and `_is_runtime_setup_required` from `InstanceKlassFlags` (has run out of bits) to here (we still have 7 extra bits left), to accommodate future `@AOTXXX` annotations.

Ioi Lam has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 10 commits:

 - @liach and @ashu-mehra comment: Renamed Klass::_is_generated_shared_class -> _is_aot_generated_class
 - Merge branch 'master' into 8366477-refactor-aot-related-flag-bits-in-klass-hpp.saved
 - Merge branch '8366475-rename-metaspace-shared-to-aot-metaspace' into 8366477-refactor-aot-related-flag-bits-in-klass-hpp
 - removed unnecessary includes
 - Redo changes in comments and tests
 - Merge branch '8366474-rename_metaspaceobj_is_shared_to_in_aot_cache' into 8366475-rename-metaspace-shared-to-aot-metaspace
 - Removed MetaspaceShared -> AOTMetaspace changes that are intended for https://github.com/openjdk/jdk/pull/27017
 - 8366477: Refactor AOT-related flag bits in klass.hpp
 - Rename MetaspaceShared -> AOTMetaspace
 - 8366474: Rename MetaspaceObj::is_shared() to MetaspaceObj::in_aot_cache()

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Changes: https://git.openjdk.org/jdk/pull/27018/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27018&range=02
  Stats: 60 lines in 7 files changed: 20 ins; 10 del; 30 mod
  Patch: https://git.openjdk.org/jdk/pull/27018.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27018/head:pull/27018

PR: https://git.openjdk.org/jdk/pull/27018