[android] Write "collator" wrappers for Expression.java

[ChrisLoer]

Follow-on for #11869: Android now supports "collator" expressions, but they're not directly exposed via the SDK. Collator expressions take a dictionary-style object as an argument, e.g.:

["collator", {"case-sensitive": false, "diacritic-sensitive": true, "locale": "en"}]

This is a new pattern so we'll have to figure out the right Java-appropriate way to wrap it.

/cc @LukasPaczos @tobrun

[tobrun]

Looking into this and noticing that the expression evaluate is expecting an object, this isn't yet supported in jni for our filter/properties conversion system (see todo here). Currently taking the approach to represent an object as Map<String, Object> where the key/value represent the fields of the object.