RFR: JDK-8306112 Implementation of JEP 445: Unnamed Classes and Instance Main Methods (Preview) [v17]

[Jim Laskey]

> Add flexible main methods and anonymous main classes to the Java language.

Jim Laskey has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 33 commits:

 - Fix missing constructor error messages and handle inner class launching
 - Merge branch 'master' into 8306112
 - Issue warning if traditional main not used.
 - Give subclass priority
 - Merge branch 'master' into 8306112
 - Requested Changes #2
 - Update VirtualParser.java
 - Merge branch 'master' into 8306112
 - Refactor source code launcher
 - Typo
 - ... and 23 more: https://git.openjdk.org/jdk/compare/bddf4838...b55f82f8

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Changes: https://git.openjdk.org/jdk/pull/13689/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13689&range=16
  Stats: 1235 lines in 28 files changed: 1071 ins; 32 del; 132 mod
  Patch: https://git.openjdk.org/jdk/pull/13689.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13689/head:pull/13689

PR: https://git.openjdk.org/jdk/pull/13689