add thanos exceptions for allowedHostFilesystem/volumeTypes

Adds required gatekeeper exceptions for Thanos cypress

Thanos helm tests should be passing now when gatekeeper is enabled.

Prior to fix (as seen in the upgrade 1st test runs):

Running helm tests for thanos...
Error: warning: Hook test thanos/templates/tests/test-ui.yaml failed: 1 error occurred:
	* admission webhook "validation.gatekeeper.sh" denied the request: [allowed-host-filesystem] HostPath volume {"hostPath": {"path": "/cypress", "type": ""}, "name": "cypress-artifacts"} is not allowed, pod: thanos-cypress-test. Allowed path: []
[volume-types] The volume type hostPath is not allowed, pod: thanos-cypress-test. Allowed volume types: ["configMap", "emptyDir", "projected", "secret", "downwardAPI", "persistentVolumeClaim"]
❌ One or more tests FAILED for thanos, enable DEBUG for more verbose output

with fix -- clean install and upgrade 2nd test runs:

Running helm tests for thanos...
✅ All tests sucessful for thanos

tests/test-values.yaml

@@ -186,6 +186,7 @@ gatekeeper:
           - nexus-repository-manager/nexus-repository-manager-cypress-test
           - sonarqube/sonarqube-cypress-test
           - tempo/tempo-cypress-test
+          - thanos/thanos-cypress-test
           - twistlock/twistlock-cypress-test
           - vault/vault-cypress-test
           # Allow kyverno test vectors for Helm test
@@ -324,6 +325,7 @@ gatekeeper:
           - nexus-repository-manager/nexus-repository-manager-cypress-test
           - sonarqube/sonarqube-cypress-test
           - tempo/tempo-cypress-test
+          - thanos/thanos-cypress-test
           - twistlock/twistlock-cypress-test
           - vault/vault-cypress-test
           # Allow kyverno test vectors for Helm test