RFR: 8367689: Revert removal of several compilation-related vmStructs fields [v2]

[Francesco Andreuzzi]

> #23782 ([JDK-8315488](https://bugs.openjdk.org/browse/JDK-8315488)) removed several vmStructs fields. A small subset was used in Async-Profiler:
> 
> CiEnv* _env
> CompileTask* _task
> ciMethod* _method
> 
> 
> I propose a small patch to bring them back. It helps third-party tools in building useful features on the JDK. For example, Async-Profiler uses these fields to display the current method being compiled in a compiler thread.

Francesco Andreuzzi has updated the pull request incrementally with six additional commits since the last revision:

 - note
 - nn
 - nn
 - cc
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Changes:
  - all: https://git.openjdk.org/jdk/pull/27318/files
  - new: https://git.openjdk.org/jdk/pull/27318/files/5bc13c6c..e8b7849d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=27318&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27318&range=00-01

  Stats: 95 lines in 14 files changed: 0 ins; 54 del; 41 mod
  Patch: https://git.openjdk.org/jdk/pull/27318.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27318/head:pull/27318

PR: https://git.openjdk.org/jdk/pull/27318