* KEP-4974: Update documentation for Endpoints deprecation
* Bring EndpointSlice docs up to date
- FQDN is not a supported AddressType
- Update documentation around `serving` vs `ready` to just explain how
it works now, without the historical context. (In particular,
describe `serving` first, and then explain `ready` as being almost
the same thing as `serving` rather than vice versa).
- Fix feature-state version macro for `terminating`
- Remove a note about some deprecated v1beta1 EndpointSlice fields
that is just confusing if you didn't know that v1beta1 had a
different topology API.
- Remove the "Comparison with Endpoints"/"Motivation" section.
* Fix up examples that still used `kubectl get endpoints`
* Replace various passing references to Endpoints with EndpointSlices
* Update main headings for Endpoints and Endpoint Slice Mirroring
* Update glossary for Endpoints deprecation
- Adds Gateway API term to the glossary.
- Adds Gateway API as reference in the addons page.
- Adds a page to the Service networking docs that explains Gateway API.
- Updates existing docs to reference the newly added Gateway API docs.
Signed-off-by: Daneyon Hansen <daneyon.hansen@solo.io>