RFR: 8315532: Compiler Implementation for Unnamed Variables and Patterns [v3]

[Aggelos Biboudis]

> This PR finalizes the feature of unnamed variables and patterns.
> 
> ---------
> ### Progress
> - [ ] Change must be properly reviewed (1 review required, with at least 1 [Reviewer](https://openjdk.org/bylaws#reviewer))
> - [x] Change must not contain extraneous whitespace
> - [x] Commit message must refer to an issue
> - [ ] Change requires CSR request [JDK-8315851](https://bugs.openjdk.org/browse/JDK-8315851) to be approved
> 
> 
> 
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> `$ git checkout pull/15649`
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> Update a local copy of the PR: \
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> 
> ### Webrev
> [Link to Webrev Comment](https://git.openjdk.org/jdk/pull/15649#issuecomment-1733906010)

Aggelos Biboudis has updated the pull request incrementally with one additional commit since the last revision:

  Address review by @mcimadamore

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/15649/files
  - new: https://git.openjdk.org/jdk/pull/15649/files/3becc945..630b128e

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15649&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15649&range=01-02

  Stats: 128 lines in 11 files changed: 41 ins; 3 del; 84 mod
  Patch: https://git.openjdk.org/jdk/pull/15649.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15649/head:pull/15649

PR: https://git.openjdk.org/jdk/pull/15649