RFR: 8307196: Dangling pointer warning for MetadataAllocationRequest

[Kim Barrett]

Please review this change to work around a false positive -Wdangling-pointer
warning from gcc13.1. The approach being taken is to suppress the warning,
with a comment describing why it's a false positive.

As with JDK-8307147 I tried various code modifications to avoid the warning,
but they were either obscure, or didn't seem reliably future-proof against
further changes in gcc's analysis.

Testing:
mach5 tier1-3 with gcc11.2 (current default in Oracle's CI)

Local (linux-x64) tier1 with gcc13.1, and verified the relevant warnings are
not reported during the build. This required disabling compiler warnings as
errors, as there are other new warnings from gcc13.1: JDK-8307210.

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

Commit messages:
 - disable metaspace warning

Changes: https://git.openjdk.org/jdk/pull/13789/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13789&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8307196
  Stats: 7 lines in 1 file changed: 7 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/13789.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13789/head:pull/13789

PR: https://git.openjdk.org/jdk/pull/13789