Test serialization/deserialization of move event coordinates

[moniika]

Test serialization/deserialization of coordinate properties for move events (Blockly.Events.Move and Blockly.Events.CommentMove).

They are not currently included in serialization tests for events because there is extra logic needed because old/new coordinates are not set in the constructor of these events, but rather than when recordNew is called (and setOldCoordinate in the case of workspace comment event).

[gonfunko]

Closing as there are now tests exercising this for both blocks and comments that were added during the serialization refactor.