RFR: Merge jdk18

[Jesper Wilhelmsson]

Forwardport JDK 18 -> JDK 19

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

Commit messages:
 - Merge remote-tracking branch 'jdk18/master' into Merge_jdk18
 - 8275830: C2: Receiver downcast is missing when inlining through method handle linkers
 - 8265317: [vector] assert(payload->is_object()) failed: expected 'object' value for scalar-replaced boxed vector but got: NULL
 - 8279379: GHA: Print tests that are in error
 - 8278966: two microbenchmarks tests fail "assert(!jvms->method()->has_exception_handlers()) failed: no exception handler expected" after JDK-8275638
 - 8278824: Uneven work distribution when scanning heap roots in G1

The webrevs contain the adjustments done while merging with regards to each parent branch:
 - master: https://webrevs.openjdk.java.net/?repo=jdk&pr=6959&range=00.0
 - jdk18: https://webrevs.openjdk.java.net/?repo=jdk&pr=6959&range=00.1

Changes: https://git.openjdk.java.net/jdk/pull/6959/files
  Stats: 161 lines in 9 files changed: 125 ins; 11 del; 25 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6959.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6959/head:pull/6959

PR: https://git.openjdk.java.net/jdk/pull/6959