Re-apply "[AArch64] Enable "sink-and-fold" in MachineSink by default (#67432)"

This re-applies commit ace20e24, which was reverted in eff4ef25.

The issues were fixed in:

  * b30765ca [AArch64] Fix an incorrect handling of debug values in
    MachineSink (#68107)

  * b454b04d [AArch64] Fix a compiler crash in MachineSink (#67705)