RFR: 8365428: Unclear comments on java.lang.invoke Holder classes [v2]

[Chen Liang]

> java.lang.invoke has a few Holder classes in DirectMethodHandle, DelegatingMethodHandle, Invokers, and LambdaForm.
> 
> Currently, the comments simply refer to "Placeholder for xxx generated ahead-of-time".
> 
> However, they carry executed bytecode and show up in flame graphs. The current comments are definitely not sufficient for their details and purposes.
> 
> To address these shortcomings, I improved the comments on the Holder classes and GenerateJLIClassesHelper to briefly describe the generation process. In addition, I improved the comments on BoundMethodHandle to provide a more efficient overview.

Chen Liang has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:

 - Merge branch 'master' of https://github.com/openjdk/jdk into doc/mh-holder-pregen
 - Ioi reviews
 - 8365428: Unclear comments on java.lang.invoke Holder classes

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/27010/files
  - new: https://git.openjdk.org/jdk/pull/27010/files/723cf749..d65a56a2

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=27010&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27010&range=00-01

  Stats: 5993 lines in 599 files changed: 3013 ins; 1284 del; 1696 mod
  Patch: https://git.openjdk.org/jdk/pull/27010.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27010/head:pull/27010

PR: https://git.openjdk.org/jdk/pull/27010