gallium: replace 16BIT_TEMPS cap with 16BIT_CONSTS

gallium: replace 16BIT_TEMPS cap with 16BIT_CONSTS

All drivers that support mediump lowering should support 16BIT_TEMPS,
but some do not also want 16b consts to be lowered.  Replace the pipe
cap in preperation to remove LowerPrecisionTemporaries.

Note: also updates reference checksums for the arm64_a630_traces job,
due to lowering more to 16b

Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6189>