[WIP] Report additional info about pauth failures

[kovdan01]

TODO:

• Move common code from StopInfoMachException and StopInfoUnixSignal to base class StopInfo.
• Handle SIGBUS and SIGTRAP if needed.
• Get proper fault address needed for comparing against current_pc; not passed to StopInfoUnixSignal but passed to StopInfoMachException as part of exc_data.
• Detect LDRAA, LDRAB. This is dependent on setting proper fault address, the code itself should be mostly identical to corresponding one in StopInfoMachException.
• Less ugly implementation of StopInfoUnixSignal::GetDescription: we already have signal description set in GetCrashReasonString->UnixSignals::GetSignalDescription and need to append pauth-related notes w/o recalculating them at every GetDescription call
• Tests
  • API tests checking output of StopInfoUnixSignal::GetDescription.
  • Ensure that tests introduced in https://reviews.llvm.org/D102428 are not broken.

This is dependent on PR68 since we need to detect pauth-enabled target via reading GNU_PROPERTY_AARCH64_FEATURE_PAUTH, so merging into dkovalev/pauth-lldb as for now.