RFR: JDK-8313796: AsyncGetCallTrace crash on unreadable interpreter method pointer [v5]

[Richard Startin]

> Makes AsyncGetCallTrace more resilient to method unloading.

Richard Startin has updated the pull request incrementally with one additional commit since the last revision:

  nullptr can't be converted to intptr_t

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Changes:
  - all: https://git.openjdk.org/jdk/pull/15193/files
  - new: https://git.openjdk.org/jdk/pull/15193/files/bfb3ff59..ad96b72f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15193&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15193&range=03-04

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/15193.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15193/head:pull/15193

PR: https://git.openjdk.org/jdk/pull/15193