RFR: 8284828: Use `os::ThreadCrashProtection` to protect AsyncGetCallTrace from crashing

[Johannes Bechberger]

Move the AsyncGetCallTrace method implementation into a separate method and wrap its call in non-assert compilation mode in `os::ThreadCrashProtection` like it is done in [JFR](https://github.com/openjdk/jdk/blob/965ea8d9cd29aee41ba2b1b0b0c67bb67eca22dd/src/hotspot/share/jfr/periodic/sampling/jfrThreadSampler.cpp#L165).
This prevents AsyncGetCallTrace from crashing on segmentation faults (but not on `guarantee`s).

If a crash is observed, then the `num_frames` field of the trace is set to `ticks_unknown_state` (-7) to signal a state that cannot be properly handled. `ticks_unknown_state` is currently also used for signaling unknown thread states but this should not be a problem, as the semantic is the same. If `num_frames` already has an error code then this error code is not changed. This helps to distinguish between errors in walking threads in Java and non-Java mode, as `num_frames` is set there before the walking to the appropriate error code.

_Thanks for @tstuefe for suggesting this._

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

Commit messages:
 - Wrap ASGCT in crash protection code

Changes: https://git.openjdk.java.net/jdk/pull/8225/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8225&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8284828
  Stats: 144 lines in 1 file changed: 87 ins; 56 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8225.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8225/head:pull/8225

PR: https://git.openjdk.java.net/jdk/pull/8225