[foreign-memaccess] RFR: 8253055: ScopedAccessException should be an Error

[Maurizio Cimadamore]

This patch turns scoped access exceptions into an error. This was suggested by @PaulSandoz, and is, I think a very good
idea; after all these exceptions are never meant to be exposed to the user, and, if that happens, it is always because
of obscure cases where the async exception raised during the handshake could not be delivered on time.

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Commit messages:
 - Revert stack depth changes
 - Turn scoped access exception into an error

Changes: https://git.openjdk.java.net/panama-foreign/pull/322/files
 Webrev: https://webrevs.openjdk.java.net/?repo=panama-foreign&pr=322&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8253055
  Stats: 53 lines in 5 files changed: 3 ins; 0 del; 50 mod
  Patch: https://git.openjdk.java.net/panama-foreign/pull/322.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-foreign pull/322/head:pull/322

PR: https://git.openjdk.java.net/panama-foreign/pull/322