RFR: 8315532: Compiler Implementation for Unnamed Variables and Patterns [v7]

[Aggelos Biboudis]

> This PR finalizes the feature of unnamed variables and patterns.

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

  Remove preview lines from a new .out file

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Changes:
  - all: https://git.openjdk.org/jdk/pull/15649/files
  - new: https://git.openjdk.org/jdk/pull/15649/files/067e358c..bd43790b

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15649&range=06
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15649&range=05-06

  Stats: 2 lines in 1 file changed: 0 ins; 2 del; 0 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