view .arcconfig @ 51424:3099f1c68afd

rust-index: remove one collect when converting back

Turns out this is slightly faster. Sending the results back to Python is still
the most costly (like 75% of the time) of the whole method, but it's about
as fast as it can be now.

hg perf::phases on mozilla-try-2023-03-22
before: 0.267114
after:  0.247101

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