gallium: Add PIPE_CAP_QUERY_TIMESTAMP_BITS

For those drivers that don't make full use of the 64 bits in
pipe_query_result.u64.

Applications will make use of it via GL_QUERY_COUNTER_BITS to handle
when the value rolls over.

Signed-off-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-By: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Reviewed-by: Emma Anholt <emma@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/10770>

docs/gallium/screen.rst

@@ -153,6 +153,8 @@ The integer capabilities:
   pipe_draw_info::start_instance.
 * ``PIPE_CAP_QUERY_TIMESTAMP``: Whether PIPE_QUERY_TIMESTAMP and
   the pipe_screen::get_timestamp hook are implemented.
+* ``PIPE_CAP_QUERY_TIMESTAMP_BITS``: How many bits the driver uses for the
+  results of GL_TIMESTAMP queries.
 * ``PIPE_CAP_TEXTURE_MULTISAMPLE``: Whether all MSAA resources supported
   for rendering are also supported for texturing.
 * ``PIPE_CAP_MIN_MAP_BUFFER_ALIGNMENT``: The minimum alignment that should be