revset: use `subset &` in `outgoing` This should give us the same benefit as elsewhere. Result is simpler (and "faster"). Outgoing is dominated by the discovery so no benchmark is provided.

revset: avoid in loop lookup in _generatorset._consumegen Python lookups are slow, so do all lookup outside of the for loop. This provide a small but still significant speedup: revset #0: 0:: 0) wall 0.063258 comb 0.060000 user 0.060000 sys 0.000000 (best of 100) 1) wall 0.057776 comb 0.050000 user 0.050000 sys 0.000000 (best of 100)

revset: reduce dict lookup in lazyset.__contains__ Avoid an extra dict lookup when we have to compute the value. No visible performance impact but this shaves the yak a few extra nanometers.