layers: Add Idx buffer alignment check to DrawState

layers: Add Idx buffer alignment check to DrawState

At vkCmdBindIndexBuffer() time, verify that offset param falls on an aligment boundary as set by indexType param. New check enum is DRAWSTATE_VTX_INDEX_ALIGNMENT_ERROR.
Removed checks for this from the driver and added a validation test and documentation for the new check.
ParamChecker has a check to verify indexType param is an acceptable value, but it's after the call so documented a TODO for ParamChecker to push this check prior to call.