Add sp_cert_multi to facilitate SP cert/key rotation #221

Job	Run time
Unit test (ubuntu-20.04, 2.1.9)	57s
Unit test (ubuntu-20.04, 2.2.10)	1m 1s
Unit test (ubuntu-20.04, 2.3.8)	53s
Unit test (ubuntu-20.04, 2.4.6)	55s
Unit test (ubuntu-20.04, 2.5.8)	32s
Unit test (ubuntu-20.04, 2.6.6)	27s
Unit test (ubuntu-20.04, 2.7.2)	25s
Unit test (ubuntu-20.04, 3.0.1)	13s
Unit test (ubuntu-20.04, 3.1)	19s
Unit test (ubuntu-20.04, 3.2)	15s
Unit test (ubuntu-20.04, jruby-9.1.17.0)	51s
Unit test (ubuntu-20.04, jruby-9.2.17.0)	52s
Unit test (ubuntu-20.04, jruby-9.3.2.0)	51s
Unit test (ubuntu-20.04, jruby-9.4.0.0)	55s
Unit test (ubuntu-20.04, truffleruby)	1m 54s
Unit test (macos-latest, 2.1.9)	2m 26s
Unit test (macos-latest, 2.2.10)	2m 52s
Unit test (macos-latest, 2.3.8)	2m 10s
Unit test (macos-latest, 2.4.6)	2m 8s
Unit test (macos-latest, 2.5.8)	1m 10s
Unit test (macos-latest, 2.6.6)	1m 7s
Unit test (macos-latest, 2.7.2)	1m 4s
Unit test (macos-latest, 3.0.1)	32s
Unit test (macos-latest, 3.1)	26s
Unit test (macos-latest, 3.2)	42s
Unit test (macos-latest, jruby-9.1.17.0)	1m 21s
Unit test (macos-latest, jruby-9.2.17.0)	1m 5s
Unit test (macos-latest, jruby-9.3.2.0)	1m 2s
Unit test (macos-latest, jruby-9.4.0.0)	52s
Unit test (macos-latest, truffleruby)	9m 51s
finish	0s
	40m 8s

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