[lld-macho] Optimize rebase opcode generation

This commit reduces the size of the emitted rebase sections by
generating the REBASE_OPCODE_DO_REBASE_ADD_ADDR_ULEB and
REBASE_OPCODE_DO_REBASE_ULEB_TIMES_SKIPPING_ULEB opcodes.

With this change, chromium_framework's rebase section is a 40% smaller
197 kilobytes, down from the previous 320 kB. That is 6 kB smaller than
what ld64 produces for the same input.

Performance figures from my M1 Mac mini:

x before
+ after

    N           Min           Max        Median           Avg        Stddev
x  10     4.2269349     4.3300061     4.2689675     4.2690016   0.031151669
+  10      4.219331     4.2914009     4.2398136     4.2448277   0.023817308
No difference proven at 95.0% confidence

Differential Revision: https://reviews.llvm.org/D130180