[llvm][MachO] Fix integer truncation in rebase/bind parsing (#89337)

`Count` and `Skip` should use `uint64_t` as they are encoded/decoded
using 64-bit ULEB128.

In `*_OPCODE_DO_*_ULEB_TIMES_SKIPPING_ULEB`, `Skip` could be encoded as
a two's complement for moving `SegmentOffset` backwards. Having a 32-bit
`Skip` truncates the encoded value and leads to a malformed
`AdvanceAmount`
and invalid `SegmentOffset` that extends past valid sections.