[clang] [llvm] [BPF] Generate BTF info using 'btf:type_tag' annotation (PR #91424)

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eddyz87 wrote:

This is a part of the following commit stack:
- https://github.com/llvm/llvm-project/pull/91422
- https://github.com/llvm/llvm-project/pull/91423
- https://github.com/llvm/llvm-project/pull/91424

https://github.com/llvm/llvm-project/pull/91424