Add sp_cert_multi to facilitate SP cert/key rotation #216

Job	Run time
Unit test (ubuntu-20.04, 2.1.9)	53s
Unit test (ubuntu-20.04, 2.2.10)	59s
Unit test (ubuntu-20.04, 2.3.8)	55s
Unit test (ubuntu-20.04, 2.4.6)	50s
Unit test (ubuntu-20.04, 2.5.8)	27s
Unit test (ubuntu-20.04, 2.6.6)	30s
Unit test (ubuntu-20.04, 2.7.2)	31s
Unit test (ubuntu-20.04, 3.0.1)	15s
Unit test (ubuntu-20.04, 3.1)	18s
Unit test (ubuntu-20.04, 3.2)	16s
Unit test (ubuntu-20.04, jruby-9.1.17.0)	52s
Unit test (ubuntu-20.04, jruby-9.2.17.0)	51s
Unit test (ubuntu-20.04, jruby-9.3.2.0)	47s
Unit test (ubuntu-20.04, jruby-9.4.0.0)	50s
Unit test (ubuntu-20.04, truffleruby)	2m 0s
Unit test (macos-latest, 2.1.9)	4m 28s
Unit test (macos-latest, 2.2.10)	2m 17s
Unit test (macos-latest, 2.3.8)	2m 34s
Unit test (macos-latest, 2.4.6)	4m 46s
Unit test (macos-latest, 2.5.8)	57s
Unit test (macos-latest, 2.6.6)	1m 5s
Unit test (macos-latest, 2.7.2)	1m 13s
Unit test (macos-latest, 3.0.1)	27s
Unit test (macos-latest, 3.1)	26s
Unit test (macos-latest, 3.2)	3m 10s
Unit test (macos-latest, jruby-9.1.17.0)	1m 19s
Unit test (macos-latest, jruby-9.2.17.0)	1m 8s
Unit test (macos-latest, jruby-9.3.2.0)	1m 18s
Unit test (macos-latest, jruby-9.4.0.0)	1m 4s
Unit test (macos-latest, truffleruby)	8m 4s
finish	0s
	45m 30s

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