Add ability to disable namespace management and augment namespace parameters when being managed

Feature request

the namespace supplied in spec.targetNamespace is created and modified by the operator but there does not seem to be any dials for augmenting labels/annotations.

Would be nice to have both the ability to augment attributes of the namespace (labels/annotations), including ones that are included by the operator to date, and the ability to disable namespace creation/management by the operator to have it use a "provided" namespace

Use case

Our cluster expectations is that all pods are members of the linkerd service mesh, and we have specified running-in-environment-with-injected-sidecars = true

linkerd has two modes of running, either with a cni plugin or via an init container that modifies ip tables. The later is incompatible with the label pod-security.kubernetes.io/enforce: restricted that the operator adds on this namespace. There are also other annotations like linkerd.io/inject: enabled that would be nice to specify at the namespace level.

In other contexts i think its desirable to have that namespace created ahead of tekton pipelines being deployed into it. One case i can think of is addition of quota management or other namespaces governances that might be wanted ahead of having pipelines deployed into it to ensure that it follows the governances of that namespace

Start by tracing how spec.targetNamespace is handled and where the operator creates or modifies that namespace. Define how namespace label and annotation augmentation, including operator-added attributes, and disabling namespace management should be represented. Done means a provided namespace can be used without operator management and managed namespaces support the requested attributes, with coverage for both modes.