phases: invalidate the phases set less often on retract boundary We already have the information to update the phase set, so we do so directly instead of invalidating the cache. This show a sizeable speedup in our `perf::unbundle` benchmark on the many-draft mozilla-try repository. ### data-env-vars.name = mozilla-try-2023-03-22-zstd-sparse-revlog # benchmark.name = hg.perf.perf-unbundle # bin-env-vars.hg.flavor = no-rust # bin-env-vars.hg.py-re2-module = default # benchmark.variants.issue6528 = disabled # benchmark.variants.revs = last-10 before: 2.055259 seconds after: 1.887064 seconds (-8.18%) # benchmark.variants.revs = last-100 before: 2.409239 seconds after: 2.222429 seconds (-7.75%) # benchmark.variants.revs = last-1000 before: 3.945648 seconds after: 3.762480 seconds (-4.64%)