RFR: 8324651: Compiler Implementation for Derived Record Creation (Preview) [v12]

[Jan Lahoda]

> This is a patch for javac, that adds the Derived Record Creation expressions. The current draft specification for the feature is:
> https://cr.openjdk.org/~gbierman/jep468/jep468-20240326/specs/derived-record-creation-jls.html
> 
> The current CSR is here:
> https://bugs.openjdk.org/browse/JDK-8328637
> 
> The patch is mostly straightforward, with two notable changes:
>  - there is a new `ElementKind.COMPONENT_LOCAL_VARIABLE`, as the specification introduces this term, and it seems consistent with `ElementKind.BINDING_VARIABLE` that was introduced some time ago.
>  - there are a bit broader changes in `Flow`, to facilitate the introduction of variables without an explicit declaration for definite assignment and effectively final computation.

Jan Lahoda has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 36 commits:

 - Merge branch 'master' into wthexp
 - Post-merge fixes.
 - Merge branch 'master' into wthexp
 - Reflecting review feedback:
   - reverting unnecessary changes in TransPatterns
   - moving the patters/withers/Model test to a more appropriate place
 - Adding tests as suggested.
 - Reflecting review feedback:
   - pre-generating the JCVarDecls in Attr, to aid Flow
   - adding a note on how the desugared code looks like
 - JavaCompiler cleanup
 - Improving the javax.lang.model for component local variables, by darcy.
 - Reflecting review feedback.
 - Merge branch 'master' into wthexp
 - ... and 26 more: https://git.openjdk.org/jdk/compare/4e5c25ee...c97eb8e6

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Changes: https://git.openjdk.org/jdk/pull/18509/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18509&range=11
  Stats: 2023 lines in 51 files changed: 1965 ins; 19 del; 39 mod
  Patch: https://git.openjdk.org/jdk/pull/18509.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18509/head:pull/18509

PR: https://git.openjdk.org/jdk/pull/18509