Improve the cache usage by filtering secrets (and other resources) that OLM are watching using label. This will reduce the number of objects in cache.

Some resources already have olm-specific labels that can simply be used directly (such as catalogsource pods) and allow this change to be backportable/backward-compatible. If that is the case, then it can be fixed and backported via BZ. Some other resources don't have pre-existing label and OLM needs to add a new label to existing objects in order to be backportable/backward-compatible.