Function resolve_dependencies 

pub fn resolve_dependencies(items: &[PackageItem]) -> Vec<DependencyInfo>

What: Resolve dependencies for the requested install set while consolidating duplicates.

Inputs:

• items: Ordered slice of packages that should be analysed for dependency coverage.

Output:

• Returns a vector of DependencyInfo records summarising dependency status and provenance.

Details:

• Resolves ONLY direct dependencies (non-recursive) for each package in the list.
• Merges duplicates by name, retaining the most severe status across all requesters.
• Populates depends_on and required_by relationships to reflect dependency relationships.