[foreign-memaccess+abi] RFR: 8301261: Add linker option for specifying uncaught exception handler

[Jorn Vernee]

This patch adds the ability to specify an uncaught exception handler for an upcall stub, and changes the uncaught exception handling code to delegate to the thread's installed uncaught exception handler when no handler is specified as well, which will also allow setting a system-wide uncaught exception handler.

For the tests: I've refactored TestUpcallException a bit. Previously the test code was found in a separate class (ThrowingUpcall). I've removed this class and moved the code into nested classes of TestUpcallException instead. Then I've added new test cases for testing the uncaught exception handler.

I also noticed that we were setting the wrong system property to control binding recipe specialization in several tests (I thought I fixed this before, but it might have been undone by a merge...). I've fixed these to set the right property, and that also revealed a small bug in the interpreted version of the UnboxAddress binding, where we weren't properly reject heap segments. I've fixed that as well.

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Commit messages:
 - don't emit condy of handler is null
 - add tests
 - WIP

Changes: https://git.openjdk.org/panama-foreign/pull/777/files
 Webrev: https://webrevs.openjdk.org/?repo=panama-foreign&pr=777&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8301261
  Stats: 378 lines in 29 files changed: 211 ins; 96 del; 71 mod
  Patch: https://git.openjdk.org/panama-foreign/pull/777.diff
  Fetch: git fetch https://git.openjdk.org/panama-foreign pull/777/head:pull/777

PR: https://git.openjdk.org/panama-foreign/pull/777