[kots] Add a pre-flight check for cert-manager

With #8785, We expect users
to install their own `cert-manager` install. This PR adds a new
pre-flight check to verify the existence of the `cert-manager`.

As there is no general way to check for the existence of `cert-manager`,
We check for the `certificates.cert-manager.io` CRD instead.

Signed-off-by: Tarun Pothulapati <[email protected]>

Author: Pothulapati

install/kots/manifests/kots-preflight.yaml

@@ -95,3 +95,11 @@ spec:
               message: The cluster must contain at least 4 cores
           - pass:
               message: There are at least 2 cores in the cluster
+    - customResourceDefinition:
+        checkName: Cert-manager is installed
+        customResourceDefinitionName: certificates.cert-manager.io
+        outcomes:
+          - fail:
+              message: Custom resource definition `certificates.cert-manager.io` was not found in the cluster. Please [install `cert-manager`](https://cert-manager.io/docs/installation/) to proceed.
+          - pass:
+              message: Cert-manager is installed and available.