st/mesa: add more fallback gallium formats for GL integer formats

st/mesa: add more fallback gallium formats for GL integer formats

The VMware driver has a limited set of integer texture formats.  We
often have to fall back to 4-component formats when 1- or 2-component
formats are missing.

This fixes about 8 integer texture Piglit tests with the VMware driver
on Linux.  We've had this code in-house for a long time but I guess it
was never up-streamed to Mesa master.

This shouldn't regress any other drivers since we're either choosing
an earlier format in the list, or failing anyway.

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