Nargo entry points should be configurable via Nargo.toml

[phated]

Problem

Currently, nargo has hardcoded logic to search for a lib.nr or main.nr file to determine a CrateType. Since the CrateType will be specified in Nargo.toml with #2073, we can decouple the paths and allow them to be configured via Nargo.toml with defaults for lib.nr or main.nr if not specified.

Happy Case

A user can override the path to their entry point file, whether it is a lib, bin, or contract.

Alternatives Considered

No response

Additional Context

No response

Would you like to submit a PR for this Issue?

Yes

Support Needs

No response

[phated]

Related to #1040 (cc @TomAFrench)