[Clang] Support typedef with btf_decl_tag attributes

[Clang] Support typedef with btf_decl_tag attributes

Previously, btf_del_tag attribute supports record, field, global variable,
function and function parameter ([1], [2]). This patch added support for typedef.
The main reason is for typedef of an anonymous struct/union, we can only apply
btf_decl_tag attribute to the anonymous struct/union like below:
  typedef struct { ... } __btf_decl_tag target_type
In this case, the __btf_decl_tag attribute applies to anonymous struct,
which increases downstream implementation complexity. But if
typedef with btf_decl_tag attribute is supported, we can have
  typedef struct { ... } target_type __btf_decl_tag
which applies __btf_decl_tag to typedef "target_type" which make it
easier to directly associate btf_decl_tag with a named type.
This patch permitted btf_decl_tag with typedef types with this reason.

 [1] https://reviews.llvm.org/D106614
 [2] https://reviews.llvm.org/D111588

Differential Revision: https://reviews.llvm.org/D110127