add support GetMultipleKeys #3975

Job	Run time
Basic Checks	1m 58s
Unit Tests	10m 33s
Integration Tests (raft)	14m 35s
Integration Tests (pvtdata)	12m 59s
Integration Tests (pvtdatapurge e2e)	22m 9s
Integration Tests (ledger)	15m 25s
Integration Tests (lifecycle)	8m 13s
Integration Tests (smartbft)	21m 41s
Integration Tests (discovery gossip devmode pluggable)	10m 6s
Integration Tests (gateway idemix pkcs11 configtx configtxlator)	21m 46s
Integration Tests (sbe nwo msp)	7m 55s
	2h 27m 20s

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