[lld-macho] Category Merger: add support for addrsig references (#90903)

When generating categories, clang sometimes will generate references in
the `.addrsig` section to the various category data items. Since we may
erase such items after merging them, we also need to remove them from
the `.addrsig` section - otherwise this will cause runtime asserts with
the `.addrsig` section trying to access invalid data.

Implementation wise, we use a hashset to keep track of all erased
`InputSection`'s and then go through all `.addrsig` sections and remove
references to any erased `InputSection`.