Fix: truffle console crash when metadata is missing in JSON artifact

[dPreininger]

PR description

As per the issue #5812 , truffle console command would throw an error and exit, if the metadata field was not present in all JSON blob files generated in the build process. The metadata field is not present in JSON files derived from Vyper source files.

Testing instructions

1. Either compile a Vyper smart contract or delete metadata field in one of the generated JSON blobs from Solidity smart contracts.
2. Run truffle migrate. IMPORTANT: do not run truffle develop, as some configurations (truffle-config.js) were not affected by this bug (see issue for more details).
3. Run truffle console. The command executes without errors.

Documentation, breaking changes and new features

This PR does not introduce any breaking changes or new features. The documentation does not need to be changed either.

[cds-amal]

Thanks for this, @dPreininger. There are two small comment nits I'd like updated.

[dPreininger]

I have committed the suggestions.

[cds-amal]

Thanks for finding and fixing this bug, @dPreininger !

[eggplantzzz]

this seems like it does the job - I wonder what limitations we have in using these artifacts when they don't contain metadata, I'm not sure where we use this field in Truffle

[dPreininger]

@eggplantzzz I have actually looked through the code and found only 2 instances of metadata being used (besides this console.js file):
packages/codec/lib/compilations/utils.ts
packages/compile-solidity/src/run.ts

and 2 more test files:
packages/compile-solidity-tests/test/metadata.ts -> this is a test file
packages/contract-schema/test/solc.js -> this is a test file

I might have missed some more usages, but it seems to me that it was only really used to filter out Console contract.