Discontinue AppVeyor CI testing (#1682) #1418

Job	Run time
Check upstream code is properly integrated	1m 4s
Check code formatting	1m 13s
Check that code passes a basic build before starting heavier tests	1m 0s
linux_arm_emulated (armhf, armhf, -DOQS_ENABLE_SIG_SPHINCS=OFF -DOQS_USE_OPENSSL=OFF -DOQS_OPT_TA...	13m 33s
linux_intel (alpine, openquantumsafe/ci-alpine-amd64:latest, -DOQS_STRICT_WARNINGS=ON -DOQS_USE_O...	5m 4s
linux_intel (alpine-openssl-all, openquantumsafe/ci-alpine-amd64:latest, -DOQS_STRICT_WARNINGS=ON...	16m 34s
linux_intel (alpine-noopenssl, openquantumsafe/ci-alpine-amd64:latest, -DOQS_STRICT_WARNINGS=ON -...	5m 0s
linux_intel (focal-nistr4-openssl, openquantumsafe/ci-ubuntu-focal-x86_64:latest, -DOQS_STRICT_WA...	3m 48s
linux_intel (jammy-std-openssl3, openquantumsafe/ci-ubuntu-jammy:latest, -DOQS_STRICT_WARNINGS=ON...	3m 32s
linux_intel (address-sanitizer, openquantumsafe/ci-ubuntu-focal-x86_64:latest, -DCMAKE_C_COMPILER...	7m 58s
	58m 46s

Provide feedback