swr/rast: Refactor api and worker event handlers.

swr/rast: Refactor api and worker event handlers.

In the API event handler we want to share information between the core
layer and the API. Specifically, around associating various ids with
different kinds of events. For example, associate render pass id with
draw ids, or command buffer ids with draw ids.

Reviewed-by: Bruce Cherniak <bruce.cherniak@intel.com>