Improve cog base image handling (#1699)
In preparation for making `--use-cog-base-image` flag the default behavior, we are adding better
handling for invalid configuration.
* Check that the combination of cuda, python and pytorch is valid before attempting to run/build the image
* Check that we are not missing flags that don't work together
Signed-off-by: Marcus Martins <marcus@replicate.com>
Co-authored-by: Zeke Sikelianos <zeke@sikelianos.com>
