Add anchor to MarkerView

[tobrun]

Google exposes customization of Anchor:

The point on the image that will be placed at the LatLng position of the marker. This defaults to the middle of the bottom of the image.

Now that #3276 landed we can implement this in MarkerView/MarkerViewOptions (vs GL Marker #2916).

[tobrun]

Note that Google maps also exposes this for InfoWindow

[tobrun]

At this point we are exposing:

PointF centerOffset;
Point infoWindowOffset;

This should be replaced with Anchor API instead:

float anchorU;
float anchorV;
float infoWindowAnchorU;
float infoWindowAnchorV;

This is how Google exposes this in their javadoc:

[tobrun]

This is how the default implementation works:

Note that the default values for u = 0.5 and v = 1.0 are used.
This results in anchoring the annotation to the bottom center.

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This is the result for u = 0 and v = 0 aka topleft:

This is the result for u = 1 and v = 1 aka bottomright:

This is the result for u = 0.5 and v = 0.5 aka center:

This is the result for u = 0 and v = 0.5:

[tobrun]

It seems that InfoWindow anchoring needs some extra work. Our current setup doesn't match how Google maps was setup. This will require some extra code to not break current exposed logic for GL based annotations.

[tobrun]

I was able to get the old InfoWindow logic working with the newer anchoring. This is currently introducing some unneeded overhead but this can only be resolved if we implement anchoring of GL based markers (else we would have a breaking API change for users using the GL based annotations).

Here you see a screenshot with anchoring in action:

• bottom left has infoWindowAnchor(1.0f, 1.0f)
• center has infoWindowAnchor(0.5f, 0.0f) (default value)
• right has infowWindowAnchor(0.0f, 0.0f)