FLEX-35280FLEX-35260 Recent changes to FLEX-35267 made it so that the y value in GridHeaderViewLayout.getHeaderIndexAt() started to be considered, when before it was simply ignored. But one caller of this function, GridColumnHeaderGroup.eventToHeaderLocations(), simply used '0' for that argument, instead of the real value, knowing that (before these changes) it wasn't being considered. Now the real value is used.
FLEX-35267 Updated unit test - made it easier to read, and now we're also testing GridColumnHeaderGroup.containsGlobalCoordinates(). For the test to pass I've improved the logic in GridHeaderViewLayout.getHeaderIndexAt() which, in turn, made a few functions redundant in GridColumnHeaderGroup. All tests currently pass.