Feat int minimization

[tnelson]

This PR implements the optimization features described here. The set-based optimization is still somewhat brittle, but the feature should be made available in preview form.

Known issues:

• Combining a partial-instance bound and a partial-instance target is restricted and needs better documentation (e.g., the lower bound of the target must be contained in the upper bound of the run).
• The hidden internal relations that convert an integer-optimization problem to a set-optimization problem persist between runs, even into runs that don't use integer optimization. (This is an architectural problem that will require a small amount of refactoring. Forge wasn't originally built to allow removing relations from the model.)

This PR also fixes the verbosity level that triggers collector spam for debugging; 5 ("HIGH") will no longer be enough.

Finally, this PR also expands the run-tests.sh script to no longer attempt to run the SMT backend tests if cvc5 is not on the path. (Aside: I don't have a lot of shell-script experience beyond the basics, so this is a place I would like to request extra review effort.)