refactor: remove indexmap

[Boshen]

The only call site that iterates through the indexmap doesn't seem to require the map to be in the order of declaration.

pnp-rs/src/lib.rs

Lines 160 to 175 in b443744

	for (name, ranges) in manifest.package_registry_data.iter_mut() {
	for (reference, info) in ranges.iter_mut() {
	let package_location = manifest.manifest_dir.join(info.package_location.clone());
	let normalized_location = util::normalize_path(package_location.to_string_lossy());
	info.package_location = PathBuf::from(normalized_location);
	if !info.discard_from_lookup {
	manifest.location_trie.insert(
	&info.package_location,
	PackageLocator { name: name.clone(), reference: reference.clone() },
	);
	}
	}
	}

[arcanis]

I think I added that when adding a clippy warning against unstable traversal, as I got quite a few mistakes due to this in other programs. That said in this particular app it's probably ok.