Use absolute path to disambiguate contract names

[nwatson22]

Closes #178
Replaces references to contracts done by name with a name qualified by the full path of the contract, e.g. contract Initializable in openzeppelin-contracts-upgradeable/contracts/proxy/utils/Initializable.sol would get the name openzeppelin-contracts-upgradeable%contracts%proxy%utils%Initializable. % is used as a separator because the names of the contracts become directory names when the proofs are saved to disk. In generated K files the K escaping would convert this to S2KopennzeppelinZSubcontractsZSubupgradeableZModcontractsZModproxyZModutilsZModInitializable-CONTRACT.

When there is a duplicate name, solc will disambiguate the files in the out directory by adding their paths as subdirectories. Our foundry.contracts function previously would just not import these. This changes is to recursively import .jsons directly under a .sol directory.

Because of this issue of the duplicates not being imported because they're in subdirectories, I don't know how to reproduce the runtime error Project contains duplicated contract names that may clash in K definitions: {contract_name} in master. However, I've added contracts with duplicate names under src/tests/integration/test-data/foundry/src/ to demonstrate that duplicate test names can be imported with the new system.

[anvacaru]

The quality-checks stage is currently failing on CI. You can run make format; make in the repo's root to format the Python files automatically and run the unit tests.