RFR: 8339686: java/foreign/TestMappedHandshake.java fails with assert(depth < max_critical_stack_depth) failed: can't have more than 10 critical frames [v2]

[Maurizio Cimadamore]

> The new test added by https://github.com/openjdk/jdk/pull/20854 fails spuriously.
> While JNI lookup is now moved into the static initializer of the `MappedMemoryUtils` class, this class might only get initialized while in the middle of a scoped context.
> 
> To address this, I created a new proxy interface, namely `MappedMemoryUtilsProxy`. This interface is used by `ScopedMemoryAccess` to call the various `force`/`load`/`isLoaded`/`unload` methods, and a singleton instance is provided inside `MappedMemoryUtils` itself, and then exposed via the `SharedSecrets` mechanism.
> 
> Crucially, `MappedMemorySegmentImpl` will now _first_ obtain a `MappedMemoryUtilsProxy` and _then_ call `ScopedMemoryAccess`. This should move all class initializer side-effects out of the scoped method context.

Maurizio Cimadamore has updated the pull request incrementally with one additional commit since the last revision:

  Drop spurious change

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/20914/files
  - new: https://git.openjdk.org/jdk/pull/20914/files/32389c43..4053014e

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=20914&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20914&range=00-01

  Stats: 1 line in 1 file changed: 0 ins; 1 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/20914.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20914/head:pull/20914

PR: https://git.openjdk.org/jdk/pull/20914