Rename CatalogSource to OperatorCatalog

[anik120]

Motivation:

CatalogSource is a hangover from OLM v0.

"Here's how you can add this operator catalog to your cluster" sounds less confusing than "Here's how you can add this catalog source to your cluster", possibly since catalogSource is trying to encompass engineering implementation details, that our customers don't need to be exposed to.

Goal:

This is proposal to change the name CatalogSource to OperatorCatalog for catalogd.

[everettraven]

Is there a reason why we can't just call it Catalog?

[anik120]

Is there a reason why we can't just call it Catalog?

In my head it's beneficial to keep words in our products's names that are brand recognizable.
Catalog also feels very generic, it could be a catalog of furnitures that someone is talking about when they're using that in a conversation. Instead if you're using OperatorCatalog in the conversation, the context is always explicit, and reinforces the brand every time it's mentioned.

cc: @dmesser in case you want to chime in

[joelanford]

I'm +1 on Catalog. The API group will include operatorframework.io