mesa: Redefine MESA_FORMAT_* in terms of PIPE_FORMAT_*.

mesa: Redefine MESA_FORMAT_* in terms of PIPE_FORMAT_*.

There are various places in Mesa where we would like to be able to
have a shared format enum between Mesa and gallium (NIR compiler's
image formats, for example, or mapping from gallium's formats to
mesa's and vice versa in st_format.c).  Rewriting all MESA_FORMAT to
PIPE_FORMAT would be disruptive and possibly more work than it's worth
(And I actually prefer MESA_FORMAT's name scheme), so for now just
make it so that there's one shared set of enum values.

The #defines here were generated by printing out from the
tests/st_format.c round-tripping loop, with the exception of 8888
formats where I hand-edited the #defines to point at the corresponding
gallium packed format define.

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