Initial annotation-based implementation

[perdasilva]

Create initial SingleNamespace and OwnNamespace install mode support that side-steps the API changes by allowing the user to specify the watch namespace via annotation.

requirements:

• must only be enabled when feature-gate is enabled
• must default to AllNamespaces install mode when not set
• should default to AllNamespaces install model when annotation is set but value is empty
• could allow switching between install modes after installation
• must not support multi- watch namespaces

[perdasilva]

done

[pgodowski]

As in the PR comment, want to understand the next steps there - e.g. it is expected that OLMv1 would introduce support for multiple operators being installed with different scopes defined on the same cluster, however the doc https://github.com/perdasilva/operator-controller/blob/main/docs/draft/howto/single-ownnamespace-install.md says:

It should be noted that, in line with v1's no multi-tenancy policy, users will not be able to install the same operator multiple times, and that in future iterations of the registry bundle format will not include installModes.

As long as this approach is just an incremental step towards allowing OLMv1 installing multiple operators with different scope, it's all good.