Improve key updating performance. #3606

Job	Run time
cmake-offline-googletest-src	4m 20s
ubuntu-latest [CC gcc; botan; shared libs on; GnuPG stable]	4m 19s
ubuntu-latest [CC clang; botan; shared libs on; GnuPG stable]	3m 59s
ubuntu-latest [CC gcc; openssl; shared libs on; GnuPG stable]	4m 5s
ubuntu-latest [CC clang; openssl; shared libs on; GnuPG stable]	3m 56s
ubuntu-20.04 [CC gcc; openssl; shared libs on; GnuPG stable]	3m 42s
ubuntu-latest [CC gcc; botan; shared libs off; GnuPG stable]	4m 14s
cmake-offline-googletest	4m 32s
system-sexpp, sexpp shared libs on, rnp shared libs on	2m 51s
system-sexpp, sexpp shared libs on, rnp shared libs off	3m 8s
system-sexpp, sexpp shared libs off, rnp shared libs on	2m 49s
system-sexpp, sexpp shared libs off, rnp shared libs off	2m 43s
package-source	27s
package	52s
debian-tests	23s
	46m 20s

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