Cache DNS responses for IpaClients #5596

Job	Run time
Release builds and tests	10m 53s
Slow tests	17m 22s
Measure coverage	28m 51s
Basic Checks	20m 9s
Additional Builds and Concurrency Tests	16m 0s
miri	4m 3s
sanitize (address)	17m 58s
sanitize (address, multi-threading)	20m 16s
sanitize (leak)	7m 42s
sanitize (leak, multi-threading)	10m 21s
	2h 33m 35s

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