Consistency + alignment pass between iOS and Android Platform Public APIs

[ianthetechie]

Before 1.0, we should take a second pass through all of the public APIs for iOS and Android to ensure they are aligned.

• The biggest area is related to observability and state models, so that's probably the first thing to do. See Swift Observability overhaul #780.
• Revisit the location subscription / provider model
• Speech (spoken instruction observers)
• Route providers