[clang][CodeGen]Fix clang crash and add bitfield support in __builtin_dump_struct

Fix clang crash and add bitfield support in __builtin_dump_struct.

In clang13.0.x, a struct with three or more members and a bitfield at
the same time will cause a crash. In clang15.x, as long as the struct
has one bitfield, it will cause a crash in clang.

Open issue: https://github.com/llvm/llvm-project/issues/54462

Differential Revision: https://reviews.llvm.org/D122248