cirrus-ci: switch from swtpm to mssim. #760

Job	Run time
test-tcti-config	14m 1s
scanbuild	6m 33s
test-coverage	5m 11s
build-test (ubuntu-20.04, gcc)	4m 23s
test-mbedtls (ubuntu-20.04)	2m 45s
build-test (ubuntu-20.04, clang)	4m 14s
test-fuzz	2m 36s
test-mbedtls (ubuntu-22.04-mbedtls-3.1)	2m 38s
build-test (fedora-32, gcc)	4m 37s
build-test (fedora-32, clang)	4m 38s
test-no-crypto-build	1m 18s
build-test (opensuse-leap, gcc)	4m 31s
coverity-test	0s
build-test (opensuse-leap, clang)	4m 34s
build-test (ubuntu-22.04, gcc)	4m 36s
build-test (ubuntu-22.04, clang)	4m 45s
build-test (alpine-3.15, gcc)	3m 57s
build-test (alpine-3.15, clang)	4m 48s
	1h 20m 5s

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