RFR: 8306767: Concurrent repacking of extra data in MethodData is potentially unsafe [v4]

[Emanuel Peter]

> I'm making sure that `allocate_bci_to_data` is only called when holding the `extra_data_lock`, so that no concurrent calls of it can ever occur.
> 
> Testing: tier1-3 and stress.

Emanuel Peter has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains five commits:

 - manual merge with master after JDK-8267532
 - more locking, still fails tho - WIP
 - adding more verification and more locking, WIP
 - add locks for jvmci calls to allocate_bci_to_data
 - 8306767

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Changes: https://git.openjdk.org/jdk/pull/16840/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16840&range=03
  Stats: 123 lines in 9 files changed: 102 ins; 9 del; 12 mod
  Patch: https://git.openjdk.org/jdk/pull/16840.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16840/head:pull/16840

PR: https://git.openjdk.org/jdk/pull/16840