RFR: Merge jdk18

[Jesper Wilhelmsson]

Forwardport JDK 18 -> JDK 19

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Commit messages:
 - Merge remote-tracking branch 'jdk18/master' into Merge_jdk18
 - 8280441: Missing "classpath exception" in several files from jdk.httpserver
 - 8279179: Update nroff pages in JDK 18 before RC

The webrevs contain the adjustments done while merging with regards to each parent branch:
 - master: https://webrevs.openjdk.java.net/?repo=jdk&pr=7203&range=00.0
 - jdk18: https://webrevs.openjdk.java.net/?repo=jdk&pr=7203&range=00.1

Changes: https://git.openjdk.java.net/jdk/pull/7203/files
  Stats: 62 lines in 10 files changed: 46 ins; 0 del; 16 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7203.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7203/head:pull/7203

PR: https://git.openjdk.java.net/jdk/pull/7203