docs: add performance.md discussing transpilers and isolated_typecheck #2217

Job	Run time
matrix-prep	3s
bats-tests (7, 7.3.2)	5m 34s
test (7, 7.3.2, 1, ubuntu, .)	40s
test (7, 7.3.2, 1, ubuntu, e2e/bzlmod)	15s
test (7, 7.3.2, 1, ubuntu, e2e/external_dep)	18s
test (7, 7.3.2, 1, ubuntu, e2e/external_dep/app)	16s
test (7, 7.3.2, 1, ubuntu, e2e/worker)	18s
test (7, 7.3.2, 0, ubuntu, .)	32s
test (7, 7.3.2, 0, ubuntu, e2e/external_dep)	13s
test (7, 7.3.2, 0, ubuntu, e2e/external_dep/app)	11s
test (7, 7.3.2, 0, ubuntu, e2e/worker)	14s
test (7, 7.3.2, 0, ubuntu, e2e/workspace)	18s
test (6, 6.5.0, 0, ubuntu, e2e/external_dep)	13s
test (6, 6.5.0, 0, ubuntu, e2e/external_dep/app)	14s
test (6, 6.5.0, 0, ubuntu, e2e/worker)	26s
test (6, 6.5.0, 0, ubuntu, e2e/workspace)	17s
conclusion	5s
	10m 7s

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