universal-lock: track version numbers for all distributions

[BurntSushi]

When creating a Lock, we currently have a todo!() when trying to extract version numbers:

uv/crates/uv-resolver/src/lock.rs

Lines 281 to 287 in e33ff95

	let version = match resolved_dist.version_or_url() {
	VersionOrUrl::Version(v) => v.clone(),
	// TODO: We need a way to thread the version number for these
	// cases down into this routine. The version number isn't yet in a
	// `ResolutionGraph`, so this will require a bit of refactoring.
	VersionOrUrl::Url(_) => todo!(),
	};

For example, when the distribution comes from a direct URL, it only has a URL and not a version number:

uv/crates/distribution-types/src/lib.rs

Lines 567 to 571 in e33ff95

	impl DistributionMetadata for DirectUrlBuiltDist {
	fn version_or_url(&self) -> VersionOrUrl {
	VersionOrUrl::Url(&self.url)
	}
	}

My understanding is that a version number exists for these distributions in their metadata, but we currently don't keep it around (I believe). We need the version number for our universal lock file, as part of #3347.