RFR: JDK-8273146: Start of release updates for JDK 19 [v8]

[Joe Darcy]

> The time to get JDK 19 underway draws nigh, please review this usual set of start-of-release updates, including CSRs for the javac and javax.lang.model updates:
> 
> JDK-8277512: Add SourceVersion.RELEASE_19
> https://bugs.openjdk.java.net/browse/JDK-8277512
> 
> JDK-8277514: Add source 19 and target 19 to javac
> https://bugs.openjdk.java.net/browse/JDK-8277514
> 
> Clean local tier 1 test runs for langtools, jdk, and hotspot.

Joe Darcy has updated the pull request incrementally with one additional commit since the last revision:

  Update symbol files to JDK 18 b26.

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/6493/files
  - new: https://git.openjdk.java.net/jdk/pull/6493/files/b1b4ae2b..88273596

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=6493&range=07
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=6493&range=06-07

  Stats: 610 lines in 3 files changed: 593 ins; 3 del; 14 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6493.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6493/head:pull/6493

PR: https://git.openjdk.java.net/jdk/pull/6493