Add additional EVP_SKEY helpers #480

Job	Run time
compiler (gcc-7, ubuntu-20.04)	4m 37s
compiler (gcc-8, ubuntu-20.04)	4m 34s
compiler (gcc-9, ubuntu-20.04)	4m 42s
compiler (gcc-10, ubuntu-20.04)	4m 36s
compiler (gcc-11, ubuntu-22.04)	4m 37s
compiler (gcc-12, ubuntu-22.04)	5m 4s
compiler (gcc-13, ubuntu-22.04, ubuntu-toolchain-r/test)	7m 26s
compiler (clang-6.0, ubuntu-20.04)	4m 44s
compiler (clang-7, ubuntu-20.04)	4m 50s
compiler (clang-8, ubuntu-20.04)	4m 56s
compiler (clang-9, ubuntu-20.04)	5m 8s
compiler (clang-10, ubuntu-20.04)	4m 53s
compiler (clang-11, ubuntu-20.04)	4m 49s
compiler (clang-12, ubuntu-20.04)	4m 48s
compiler (clang-13, ubuntu-22.04)	5m 14s
compiler (clang-14, ubuntu-22.04)	5m 11s
compiler (clang-15, ubuntu-22.04, jammy)	5m 15s
compiler (clang-16, ubuntu-22.04, jammy)	5m 18s
compiler (clang-17, ubuntu-22.04, jammy)	5m 29s
	1h 36m 11s

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