Apply the AES-GCM unroll8 optimisation to Microsoft Azure Cobalt 100 #2011

Job	Run time
basic_clang	5m 11s
basic_gcc	5m 1s
check_docs	59s
check_update	1m 13s
check-ansi	2m 25s
address_ub_sanitizer	10m 7s
enable_non-default_options	4m 7s
full_featured	5m 31s
fuzz_tests	2m 57s
memory_sanitizer	19m 3s
minimal	2m 24s
no-deprecated	4m 42s
no-legacy	5m 5s
non-caching	16m 11s
no-shared-macos	9m 57s
no-shared-ubuntu	3m 56s
self-hosted (freebsd-13.2)	1s
threads_sanitizer	5m 20s
self-hosted (ubuntu-arm64-22.04)	1s
external-test-cf-quiche	3m 35s
external-test-pyca (1.51.0, 3.9)	8m 32s
external-tests	10m 44s
legacy	3m 57s
out-of-readonly-source-and-install-macos	8m 53s
out-of-readonly-source-and-install-ubuntu	6m 54s
	2h 26m 46s

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