Change behavior of watchNamespaces on contourDeployment to not include gateway's namespace by default

[lubronzhan]

Please describe the problem you have
[A clear, concise, description of the problem you are facing. What is the problem that feature X would solve for you?]
Follow up on #6073
If watchNamespaces doesn't include the gateway's namespace, either create role with minimum permission or error out on Gateway that it should include gateway's namespace .
Instead of automatically add Gateway's namespace to watchNamespaces.

[lubronzhan]

1. provision minimum permissions.
2. error out on gateway
   Hi @skriss which way do you prefer?

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This bot triages Issues according to the following rules:

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[github-actions]

The Contour project currently lacks enough contributors to adequately respond to all Issues.

This bot triages Issues according to the following rules:

• After 60d of inactivity, lifecycle/stale is applied
• After 30d of inactivity since lifecycle/stale was applied, the Issue is closed

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[github-actions]

The Contour project currently lacks enough contributors to adequately respond to all Issues.

This bot triages Issues according to the following rules:

• After 60d of inactivity, lifecycle/stale is applied
• After 30d of inactivity since lifecycle/stale was applied, the Issue is closed

You can:

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