chore: Migrate to sets.Set[string] when possible #8862

Job	Run time
e2e tests (v1.25.x, ./test/conformance, latest, no-mesh)	10m 15s
e2e tests (v1.25.x, ./test/conformance, latest, ambient)	13m 14s
e2e tests (v1.25.x, ./test/e2e, latest, no-mesh)	13m 33s
e2e tests (v1.25.x, ./test/e2e, latest, ambient)	9m 5s
e2e tests (v1.26.x, ./test/conformance, latest, no-mesh)	12m 37s
e2e tests (v1.26.x, ./test/conformance, latest, ambient)	13m 48s
e2e tests (v1.26.x, ./test/e2e, latest, no-mesh)	11m 18s
e2e tests (v1.26.x, ./test/e2e, latest, ambient)	8m 52s
e2e tests (v1.27.x, ./test/conformance, latest, no-mesh)	9m 27s
e2e tests (v1.27.x, ./test/conformance, latest, ambient)	12m 49s
e2e tests (v1.27.x, ./test/e2e, latest, no-mesh)	13m 59s
e2e tests (v1.27.x, ./test/e2e, latest, ambient)	9m 25s
	2h 18m 22s

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