fixup! x509_vfy.c and x509_lu.c: refactor find_issuer(), X509_STORE_C… #2288

Job	Run time
basic_gcc	5m 56s
check_docs	57s
basic_clang	5m 53s
check_update	1m 16s
check-ansi	2m 32s
minimal	2m 34s
no-deprecated	5m 18s
self-hosted	0s
address_ub_sanitizer	11m 1s
enable_non-default_options	4m 48s
no-shared-ubuntu	4m 30s
full_featured	6m 11s
fuzz_tests	2m 59s
memory_sanitizer	18m 31s
non-caching	12m 52s
no-shared-macos (macos-13)	9m 8s
threads_sanitizer	5m 47s
no-shared-macos (macos-14)	4m 0s
external-tests-misc	7m 48s
external-tests-providers	8m 39s
external-tests-pyca (1.51.0, 3.9)	7m 23s
legacy	4m 40s
no-legacy	5m 45s
out-of-readonly-source-and-install-macos (macos-13)	12m 27s
out-of-readonly-source-and-install-ubuntu	7m 34s
out-of-readonly-source-and-install-macos (macos-14)	6m 34s
	2h 45m 3s

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