[clang-format] add support for branch attribute macros

https://github.com/llvm/llvm-project/issues/49184

clang-format doesn't handle the use of AttributeMacros where `[[unlikely]]` / `[[likely]]` could be used in `if` statements

This was not covered in the original commit {{D80144}}

Fixes #49184

Reviewed By: curdeius, owenpan

Differential Revision: https://reviews.llvm.org/D115865