[mono][llvm] Fully support .NET exceptions with LLVM on x64, x86, arm64, arm32

[imhameed]

• Create a Mono-specific EH personality, to support associating outlined filter functions with individual catchpad or landingpad instructions (by scanning their IR parameter lists for constant function pointers)
• Use llvm.localescape to mark filter-captured values
• Translate exception filters into outlined filter functions
• Support nested clauses either by:
  • Using a scheme to encode nested filters using landingpad, or
  • Using catchswitch, catchpad, and cleanuppad, and removing Windows-specific assumptions associated with these IR ops found during testing
• Update the Mono unwinder to support all of the above

Also see:

• [mono][llvm] Support exception filters #54185
• [mono][llvm] Support nested EH clauses #54176

[SamMonoRT]

cc @vargaz

[jandupej]

Simulations show that the performance and binary size benefits would be minimal. Closing.