gallium: add PIPE_QUERY_OCCLUSION_PREDICATE_CONSERVATIVE

gallium: add PIPE_QUERY_OCCLUSION_PREDICATE_CONSERVATIVE

To be able to properly distinguish between GL_ANY_SAMPLES_PASSED
and GL_ANY_SAMPLES_PASSED_CONSERVATIVE.

This patch goes through all drivers, having them treat the two
query types identically, except:

1. radeon incorrectly enabled conservative mode on
   PIPE_QUERY_OCCLUSION_PREDICATE. We now do it correctly, only
   on PIPE_QUERY_OCCLUSION_PREDICATE_CONSERVATIVE.
2. st/mesa uses the new query type.

Fixes dEQP-GLES31.functional.fbo.no_attachments.*

Reviewed-by: Marek Olšák <marek.olsak@amd.com>