Runtime Style MyLocationView Plugin

[tobrun]

The idea for this plugin is using Runtime Styling to replace current MyLocationView implementation. @cammace started of this work in mapbox/mapbox-gl-native#7516. Instead of merging it to the main SDK, we could also expose this as a plugin and let the SDK rely on it instead. With a SemVer release we could extract the implementation completely in a separate plugin.

[cammace]

#22 has been merged into master!