RFR: 8320276: Improve class initialization barrier in TemplateTable::_new [v4]

[Matias Saavedra Silva]

> The class initialization barrier in TemplateTable::_new fast path check ensures that the class being instantiated is fully initialized. It can be improved by introducing additional fast path check when current thread is initializer thread as MacroAssembler::clinit_barrier() does. It avoids repeated calls into interpreter runtime for classes being initialized. This patch adds the optimization for x86 and aarch64. Verified with tier 1-5 tests.
> 
> This change was tested with Spring Petclinic which reported the following startup times:
> 
> Clean build:   #### Booted and returned in 161941ms
> Patched build: #### Booted and returned in 160657ms

Matias Saavedra Silva has updated the pull request incrementally with one additional commit since the last revision:

  Added comment to remaining platforms

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Changes:
  - all: https://git.openjdk.org/jdk/pull/17006/files
  - new: https://git.openjdk.org/jdk/pull/17006/files/51a0ce10..18f17cd9

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=17006&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=17006&range=02-03

  Stats: 2 lines in 2 files changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/17006.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17006/head:pull/17006

PR: https://git.openjdk.org/jdk/pull/17006