We ran into a couple of problems with the implementation of `getCurrentPosition` on Android:
  - It sometimes returns an inaccurate location
  - It times out when `enableHighAccuracy` is `true` (facebook#7495)

This change improves `getCurrentPosition` for both of the above problems. Instead of calling `requestSingleUpdate` it now calls `requestLocationUpdates` so it can receive multiple locations giving it an opportunity to pick a better one. Unlike `requestSingleUpdate`, this approach doesn't seem to timeout when `enableHighAccuracy` is `true`.

**Test plan (required)**

Verified in a test app that `getCurrentPosition` returns a good location and doesn't timeout when `enableHighAccuracy` is `true`. Also, my team has been using this change in our app in production.

Adam Comella
Microsoft Corp.