RFR: JDK-8273146: Start of release updates for JDK 19

[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.

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Commit messages:
 - Add --release 18 information. Good tier1 test results.
 - JDK-8273146: Start of release updates for JDK 19

Changes: https://git.openjdk.java.net/jdk/pull/6493/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6493&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8273146
  Stats: 3242 lines in 67 files changed: 3202 ins; 0 del; 40 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