overlays: hide commands and flags

[rsteube]

Request

Overlays are added to existing completion which implicitly sets CARAPACE_LENIENT.
For completers defined with carapace however it should be possible to truly merge it (at least to a degree).
E.g. set commands or flags hidden that aren't really used to reduce complexity of tools like git.

Proposed solution

No response

Anything else?

No response