test: add upgrade tests to verify operator forward compatibility #783

Job	Run time
fuzz_specs	5m 6s
bundle	1m 41s
lint	2m 21s
helm-test	54s
build_and_test	5m 37s
compat-e2e-test (maximal-k8s-all-deploy-methods, v1.35.1, 26.3, test-compat-e2e)	11m 57s
compat-e2e-test (olm-deploy-method, v1.28.15, 26.3, test-compat-e2e-olm)	9m 54s
compat-e2e-test (operator-upgrade, v1.30.13, 26.3, test-compat-e2e-upgrade)	8m 43s
compat-e2e-test (supported-clickhouse-compatibility, v1.30.13, 26.3,26.2,26.1,25.8, test-compat-e...	13m 36s
compat-e2e-test (minimal-k8s-all-deploy-methods, v1.28.15, 26.3, test-compat-e2e)	11m 1s
check-crd-compat	1m 53s
e2e-test (2)	12m 46s
e2e-test (1)	16m 20s
e2e-test (3)	17m 31s
e2e-test (4)	18m 0s
All CI checks passed	3s
e2e-report	8s
openshift-compat	0s
	2h 17m 31s

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