Move _containsPoint method to CircleMarker for canvas renderer

CircleMarker is the parent of Circle as of 508a75f7a836a0a5bd1e9472cb09434183046860 and should have _containsPoint instead.
Fixes no method '_containsPoint' error when hovering on a map with a CircleMarker.
Merge pull request #2480 from adimitrov/patch-1

Move _containsPoint method to CircleMarker for canvas renderer