[clang] [llvm] [DebugInfo] Use DW_op_bit_piece for structured bindings of bitfields (PR #85665)

[J. Ryan Stinnett via cfe-commits]

jryans wrote:

It would be great to add a few notes to document this additional op in the [`DIExpression` list of ops](https://llvm.org/docs/LangRef.html#diexpression). It would be especially good for those added docs to clarify the difference between this and `DW_OP_LLVM_fragment`. (I do understand that this `DW_OP_bit_piece` op is part of standard DWARF, and there are already some standard DWARF ops we use that are missing from those docs already, but even with that in mind ... it would be great to have new docs added for this additional op.)

https://github.com/llvm/llvm-project/pull/85665