✨ Imports with namespacing, pub/use

[LesterEvSe]

Motivation

The main goal of this PR is to enable an analogue of the OpenZeppelin library to exist in the SimplicityHL ecosystem. By introducing official compiler support for imports, we significantly increase code reusability and speed up application development. For projects heavily focused on security, this also allows developers to eventually "flatten" the code and audit all functions without external dependencies.

Checklist

• Visibility: Added pub and pub use to control local scope versus re-exporting.
• Import Syntax: Implemented parsing and resolution for use m::name; and explicit aliasing (as).
• Collision Handling: Enforced strict errors for local scope collisions, utilizing C3 linearization for resolving re-export conflicts.
• Transitive Dependencies: Add support for libraries importing other libraries.
• Documentation: Сode comments are updated accordingly.
• Quality Assurance: Code is formatted, all tests pass, and CI shows no errors.

[apoelstra]

CI is failing. Also, can you add a description or motivation to this PR?

[LesterEvSe]

CI is failing. Also, can you add a description or motivation to this PR?

I have updated the main PR description to include the detailed motivation for issue #155 and a technical breakdown of the import semantics introduced here.

Regarding the failing CI, @Sdoba16 and I are looking into that now. It will be fixed soon.

[apoelstra]

6c34920 needs rebase

[apoelstra]

Also, I would recommend splitting this up into multiple PRs.

In 3016ca2:

This has unrelated clippy changes. But otherwise it's unobjectionable since it just adds some keywords that we definitely want to use.

In 1310a57:

This has a ton of lockfile noise that is unrelated to the new tempfile dependency.

Also, concept NACK adding tempfile. I've had a ton of trouble with that dependency in the past. If you want to use a dependency for this please use xshell, or alternately just roll your own (which I don't really recommend, but it'd be better than using tempfile).

I would suggest adding the new tempdir testing infrastructure in a separate commit from the actual changes. (These sorts of test infra changes can also go in their own "prepare for imports" PR.)