meta: Fix saving the program pipeline state

meta: Fix saving the program pipeline state

This code was broken in some odd ways before.  Too much state was being
saved, it was being restored in the wrong order, and in the wrong way.
The biggest problem was that the pipeline object was restored before
restoring the programs attached to the default pipeline.

Fixes a regression in the glean texgen test.

v3: Fairly significant re-write.  I think it's much cleaner now, and it
avoids a bug with some meta ops that use shaders (reported by Chia-I).

v4: Check Pipeline.Current against NULL instead of Pipeline.Default.
Suggested by Chia-I.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Chia-I Wu <olv@lunarg.com>