Add sp_cert_multi to facilitate SP cert/key rotation #207

Job	Run time
Unit test (ubuntu-20.04, 2.1.9)	53s
Unit test (ubuntu-20.04, 2.2.10)	1m 0s
Unit test (ubuntu-20.04, 2.3.8)	57s
Unit test (ubuntu-20.04, 2.4.6)	51s
Unit test (ubuntu-20.04, 2.5.8)	24s
Unit test (ubuntu-20.04, 2.6.6)	26s
Unit test (ubuntu-20.04, 2.7.2)	25s
Unit test (ubuntu-20.04, 3.0.1)	15s
Unit test (ubuntu-20.04, 3.1)	13s
Unit test (ubuntu-20.04, 3.2)	13s
Unit test (ubuntu-20.04, jruby-9.1.17.0)	52s
Unit test (ubuntu-20.04, jruby-9.2.17.0)	56s
Unit test (ubuntu-20.04, jruby-9.3.2.0)	47s
Unit test (ubuntu-20.04, jruby-9.4.0.0)	49s
Unit test (ubuntu-20.04, truffleruby)	2m 0s
Unit test (macos-latest, 2.1.9)	2m 24s
Unit test (macos-latest, 2.2.10)	2m 6s
Unit test (macos-latest, 2.3.8)	2m 10s
Unit test (macos-latest, 2.4.6)	2m 35s
Unit test (macos-latest, 2.5.8)	1m 0s
Unit test (macos-latest, 2.6.6)	1m 17s
Unit test (macos-latest, 2.7.2)	59s
Unit test (macos-latest, 3.0.1)	34s
Unit test (macos-latest, 3.1)	32s
Unit test (macos-latest, 3.2)	31s
Unit test (macos-latest, jruby-9.1.17.0)	1m 27s
Unit test (macos-latest, jruby-9.2.17.0)	1m 9s
Unit test (macos-latest, jruby-9.3.2.0)	1m 16s
Unit test (macos-latest, jruby-9.4.0.0)	1m 6s
Unit test (macos-latest, truffleruby)	5m 5s
finish	0s
	35m 12s

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