Enabling option to ignore namespaces

[enxebre]

What would you like to be added (User Story)?

As a cluster service provider managing a multi-tenant environment I would like to setup my capi controllers to ignore some namespaces

Detailed Description

In a multi-tenant environment where multiple capi controllers are running I'd like to ignore some well known namespaces that might be watched by different tenant.
This should be possible by exposing a new option for "excluded-namespaces" and let the manager cache to filter out by field

			DefaultFieldSelector: fields.AndSelectors(
				fields.OneTermNotEqualSelector("metadata.namespace", "foo"),
				fields.OneTermNotEqualSelector("metadata.namespace", "bar")),

Anything else you would like to add?

No response

Label(s) to be applied

/kind feature
One or more /area label. See https://github.com/kubernetes-sigs/cluster-api/labels?q=area for the list of labels.

[k8s-ci-robot]

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[nrb]

Would you like to see this in addition to #11192?

The options appear mutually exclusive in use. Otherwise, there would need to be logic to handle/error when a namespace appears in both sets.