Add cert-manager as part of registry operator integration test setup

[michael-valdron]

Which area/kind this issue is related to?

/kind task

/area registry

Issue Description

Currently, the deployment of the cert-manager is not part of the setup process for registry operator integration test suite. This is needed if target registry operator has webhooks enabled and therefore should deploy cert-manager if webhooks are enabled.

Acceptance Criteria

• Include setup implementation that deploys cert-manager if ENABLE_WEBHOOKS=true
  • See setup function: tests/integration/cmd/devfileregistry_test.go#L36