RFR: 8297967: Make frame::safe_for_sender safer [v2]

[Johannes Bechberger]

On Thu, 1 Dec 2022 19:21:54 GMT, Johannes Bechberger <duke at openjdk.org> wrote:

>> Makes frame::safe_for_sender safer by using os::is_readable_pointer to check the location of the return address.
>
> Johannes Bechberger has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Imrove fix, thanks Martin

My new version just uses `SafeFetchN` in the place where I consistently get segfaults in my fuzzer and it works.

The issue might happen when ASGCT (and my ASGST for which I wrote a fuzzer) are called with modified sp and fp, which async-profiler might do.

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

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