GNU3 Demangler: implement new construct support

New special-name and type demangling:
- GTt/GTn: GCC transaction clone symbols
- TH/TW: TLS init and wrapper functions
- Tc: covariant return thunks with dual call-offset parsing
- Demangle _block_invoke symbols (Clang/Apple block invocations)
- Intel Vector Function ABI (_ZGV) with ISA, mask, vlen, parameter
  kind parsing; z/Z guard variable disambiguation
- Vendor-extended type (U <source-name>) for Objective-C block pointers
- Lowercase vendor type (u <source-name>) for __remove_cvref etc.
- GR <object name> reference temporary demangling
- macOS $tlv$init thread-local variable initializer suffix
- Fix typeinfo rendering to avoid duplicated name in output

New operator and constructor support:
- ABI tag (B <source-name>) consumption in DemangleUnqualifiedName,
  DemangleNestedName, and DemangleFunction
- CI1/CI2 inheriting constructors with m_lastName save/restore
- M data-member-prefix in DemangleNestedName for lambdas in
  data member initializers
- operator<=> (spaceship) in GetOperator and DemangleUnqualifiedName

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: plafosse