Treat warnings as warnings by default (rather than errors)

[jfecher]

Problem

Currently nargo treats warnings as errors by default. This is not only opposite to how other compilers (notably rustc and clang/gcc) handle warnings, but also leads to a few issues:

• Deprecation warnings are errors by default, which causes more friction than intended when deprecating features.
• Unused variables prevent compilation by default.
• There is no indication that the above two errors were originally warnings that were treated as errors. Thus, unless users are very familiar with the compiler they are usually lead to stop and fix the issues rather than passing the --allow-warnings flag.

Happy Case

Noir & Nargo should instead switch to enabling warnings by default and only treating them as errors when a new --deny-warnings flag is passed. The old --allow-warnings flag should be removed.

The name --deny-warnings was chosen to match the name of the same flag in rustc.

Alternatives Considered

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Additional Context

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Would you like to submit a PR for this Issue?

Yes

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