Default to installing the TLS CA into the operator's target namespace

[nightkr]

Description

See stackabletech/issues#498. OLM manifests are generated from the Helm charts, so fixing it in one should fix it in the other.

Note that this is a breaking change, existing users will need to either --set secretClasses.tls.caSecretNamespace=default or copy their CA secret across (kubectl -n default get secret/secret-provisioner-tls-ca -o json | jq '.metadata.namespace = "stackable-operators"' | kubectl create -f-).

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[razvan]

This prompted me to have a look at what we've done with 24.3 and it looks like default is hard coded there too.

Then I generated the manifests from this branch and saw that "default" is also used. This is understandable because there is no namespace set at the time when we generated the manifests.

So I think that this is a good fix for Helm but not for OLM where we probably need to interpolate the namespace from the environment at the installation time (or something like that).

I added a new task to this epic: stackabletech/issues#561

[nightkr]

This is still going to leave us in a better spot for OLM too though than we were in before, right? At least it would align with the default settings.

[razvan]

lgtm but maybe remove the Fixes reference to the issue before merging so that it's not closed automatically.