feat: implement FindCandidatePersistentCacheParents for scheduling persistent cache task #1805

Job	Run time
e2e_tests (normal)	44m 10s
e2e_tests (concurent-back-source)	48m 31s
e2e_tests (disable-seed-peer)	21m 20s
e2e_tests (ipv6)	43m 29s
e2e_tests (split-running-tasks)	43m 13s
e2e_tests (cache-list-metadata)	42m 11s
e2e_tests (write-buffer-size)	39m 34s
	4h 42m 28s

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