chore(android): `KMManager.getLexicalModelInfo()` should return `LexicalModel` instead of hashmap

Currently `KeyboardPickerActivity.getLexicalModelInfo()` and `KMManager.getLexicalModelInfo()` return a hashmap with key/value pairs. We should improve that to return a `LexicalModel` type.

A similar change was made for keyboards in Keyman 14.

Should also update the documentation in `android/docs/engine/KMManager/getLexicalModelInfo.md`.

Start with KeyboardPickerActivity.getLexicalModelInfo() and KMManager.getLexicalModelInfo(), then inspect the similar keyboard change made in Keyman 14. Update android/docs/engine/KMManager/getLexicalModelInfo.md alongside the API change. Done means both methods return LexicalModel rather than a hashmap and the documentation matches.

Written by the indexing model from the issue text.