[jdk17u-dev] RFR: 8268364: jmethod clearing should be done during unloading

[Kerem Kat]

Clean backport of [8268364](https://bugs.openjdk.org/browse/JDK-8268364).

It fixes crashes when accessing jmethodIDs of a class being unloaded.

Here is the reproducer that crashes JVM in ~1 second without the patch, but works fine with it: [gist](https://gist.github.com/krk/a0800bac5bc5a01709be85637285a965).

This fix also resolves the issue reported at https://github.com/async-profiler/async-profiler/issues/974 for Java 17.

**Additional testing**: release and fastdebug with `JTREG_KEYWORDS="!headful & !external-dep & !printer"`, no new test failures with the patch.

To run the repro:


javac Main.java
gcc -shared -I"$JAVA_HOME/include" -I"$JAVA_HOME/include/linux" -fPIC repro.cpp -orepro.so

java -agentpath:"$(pwd)/repro.so" -Xmx100m Main

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

Commit messages:
 - Backport 3d84398d128bb2eed6280ebbc3f57afb3b89908f

Changes: https://git.openjdk.org/jdk17u-dev/pull/2839/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=2839&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8268364
  Stats: 36 lines in 2 files changed: 20 ins; 13 del; 3 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/2839.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/2839/head:pull/2839

PR: https://git.openjdk.org/jdk17u-dev/pull/2839