[SelectionDAG] Add space-optimized forms of OPC_CheckComplexPat (#73310)

We record the usage of each `ComplexPat` and sort the `ComplexPat`s
by usage.

For the top 8 `ComplexPat`s, we will emit a `OPC_CheckComplexPatN`
to save one byte.

Overall this reduces the llc binary size with all in-tree targets by
about 89K.