`foundry-list.check` Makefile rule erases `tests/foundry/out/ag_proofs`, which it relies on

The Makefile rule tests/foundry/foundry-list.check has tests/foundry/out as an indirect dependency, so when I make it with -B, it erases the tests/foundry/out/ag_proofs directory, and this makes it easy to waste a lot of time by running this rule by mistake because in order to regenerate the foundry-list test file all the proofs in the test-foundry-prove need to be re-run.

Ideally we'd have some way for make to be able to tell if test-foundry-prove needs to be rerun and make this a dependency of tests/foundry/foundry-list.out, but if that's not possible, I think we should move everything currently in tests/foundry/out into its own directory and have tests/foundry/out be only for the generated JSON files.

Start with the Makefile rule tests/foundry/foundry-list.check and inspect how tests/foundry/out and tests/foundry/out/ag_proofs are declared as dependencies. Reproduce the behavior with make -B, then determine whether test-foundry-prove can be made an explicit dependency or whether generated proof artifacts should move to a separate directory. Done means the rule no longer removes proofs it relies on.