Update template to support watch namespace

[rahtr]

As the controller runtime supports watching namespaces, we would need to add a support to watch namespaces other than where the controller is deployed. This is a common use case for multi-tenant K8s environments. This PR introduces a watchNamespace flag which lets user define the namespaces to be watched by the controller. If left blank, it would take the release namespace.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[ack-prow]

Hi @rahtr. Thanks for your PR.

I'm waiting for a aws-controllers-k8s member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[jaypipes]

Sure, fine with me. Thanks @rahtr!

[a-hilaly]

/ok-to-test

[a-hilaly]

nice addition, thank you @rahtr!
/lgtm

[ack-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: A-Hilaly, jaypipes, rahtr

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