RFR: 8297967: Make frame::safe_for_sender safer [v3]

[Johannes Bechberger]

> Makes frame::safe_for_sender safer by using os::is_readable_pointer to check the location of the return address.

Johannes Bechberger has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR. The pull request contains one new commit since the last revision:

  Make frame::safe_for_sender safer with SafeFetch

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Changes:
  - all: https://git.openjdk.org/jdk/pull/11461/files
  - new: https://git.openjdk.org/jdk/pull/11461/files/a8903005..f7762551

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=11461&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=11461&range=01-02

  Stats: 26 lines in 4 files changed: 5 ins; 16 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/11461.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11461/head:pull/11461

PR: https://git.openjdk.org/jdk/pull/11461