RFR: 8369219: JNI::RegisterNatives can cause a memory leak in CodeCache [v2]

[Francesco Andreuzzi]

> I propose to amend the check in `nmethod::is_cold` to allow not-entrant native `nmethod` instances to be collected during GC.
> 
> Passes tier1 and tier2 (fastdebug).

Francesco Andreuzzi has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains 10 additional commits since the last revision:

 - nn
 - Merge branch 'master' into JDK-8369219
 - trigger
 - nn
 - othervm
 - stuff
 - comments and fix test
 - cc
 - fix check
 - fix and test

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/27742/files
  - new: https://git.openjdk.org/jdk/pull/27742/files/ab6b8051..b3eae893

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=27742&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27742&range=00-01

  Stats: 92 lines in 7 files changed: 81 ins; 8 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/27742.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27742/head:pull/27742

PR: https://git.openjdk.org/jdk/pull/27742