[lld][MachO] Add first bits to support special symbols

This diff adds first bits to support special symbols $ld$previous* in LLD.
$ld$* symbols modify properties/behavior of the library
(e.g. its install name, compatibility version or hide/add symbols)
for specific target versions.

Test plan: make check-lld-macho

Differential revision: https://reviews.llvm.org/D103505