Address contracts-bedrock linter and compiler warnings

[maurelian]

The contracts-bedrock packages print a ton of warnings when running either yarn build or yarn lint:contracts.

Spec:

We should address these warnings, and tighten up our solhint config so that all warnings become errors (we're clearly not paying attention to warnings, so they are pointless).

Suggested approach: break the work up into a few PRs. For a given PR you might:

• fix all instances of a specific warning across multiple files
• fix all warnings in a specific file

[shastings8]

Agrred

[smartcontracts]

No more compiler warnings in contracts-bedrock, closing!