Remove duplicate implementations of some DSA/ECDSA functions #3695

Job	Run time
cmake-offline-googletest-src	4m 6s
cmake-offline-googletest	4m 7s
system-sexpp, sexpp shared libs on, rnp shared libs on	2m 52s
package-source	40s
system-sexpp, sexpp shared libs on, rnp shared libs off	3m 4s
system-sexpp, sexpp shared libs off, rnp shared libs on	3m 2s
system-sexpp, sexpp shared libs off, rnp shared libs off	2m 42s
ubuntu-latest [CC gcc; botan; shared libs on; GnuPG stable]	4m 27s
ubuntu-latest [CC clang; botan; shared libs on; GnuPG stable]	4m 19s
ubuntu-latest [CC gcc; openssl; shared libs on; GnuPG stable]	4m 0s
ubuntu-latest [CC clang; openssl; shared libs on; GnuPG stable]	4m 21s
ubuntu-20.04 [CC gcc; openssl; shared libs on; GnuPG stable]	3m 53s
ubuntu-latest [CC gcc; botan; shared libs off; GnuPG stable]	3m 59s
package	1m 5s
debian-tests	16s
	46m 53s

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