[iOS] Merge the language/keyboard info from local kmp.json with the cloud catalog

Follow-on to #1459
> 2. Merge the language/keyboard info with the cloud catalog so the user can select a different language for the keyboard.

After keyboards are installed via ad-hoc .kmp packages, the language info needs to be merged with cloud catalog.

- [ ] Merge keyboard/language lists
- [ ] If device is offline, still show options to install languages that are available in kmp.json

Start by reading the context in issue #1459 and inspecting the iOS code that loads local kmp.json and the cloud catalog. Trace how keyboard and language lists are built, including the offline path. Done means the lists are merged and offline users can still see installable languages from kmp.json.

Written by the indexing model from the issue text.