Support partial matches in contract verifier

[perekopskiy]

🌟 Feature Request

📝 Description

Please first read about full vs partial matches for contract verification here. Currently contract verifier support only full matches. This request is for supporting partial matches. Verification logic should be updated so that if a full match wasn't found but there is a partial one then the request is persisted and API exposes its data. Also, if a contract is partially verified it should be possible to replace its verification info if some full match request comes in, but not vice versa.

🤔 Rationale

Partial match is useful when the original source code was lost after deployment but developer managed to replicate it apart from metadata. Also, etherscan performs only partial match so devs get used to it. There are cases when only partial match verification is possible without adding a new feature to contract verifier, e.g. when contract's libraries are linked dynamically.

📋 Additional Context

After it's done on backend side it would be nice to display verification type on frontend