[clang] [Clang]P3726R2: Adjustments to Union Lifetime Rules (PR #185830)

[Timm Baeder via cfe-commits]

tbaederr wrote:

Changes for the bytecode interpreter: https://gist.github.com/tbaederr/06ee17e47a7c1f1a3c3577d848195838 that makes `test/SemaCXX/cxx26-start-lifetime.cpp` work. It doesn't do any error checking in the builtin handler but that _seems_ untested in the current interpreter.

https://github.com/llvm/llvm-project/pull/185830