fix(resolver,config): remove references to root package in override dependencies

[mkatychev]

Currently having a "workspace" level wkg.toml is not possible since for any package being built, they will also show up as a dependency in the config:

# wkg.toml
[overrides]
"namespace:foo" = { path = "./foo" }
"namespace:bar" = { path = "./bar" }

$ wkg wit build --wit-dir ./foo/

Error: failed to merge package from directory `.`

Caused by:
    attempting to re-add package `namespace:foo@7.2.0` when it's already present in this `Resolve`

[mkatychev]

Not sure if this or perhaps resolve_dependencies is the best place to handle this case but this should apply to local or registry packages regardless if the dependency name+namespace+version match that of the root:

wasm-pkg-tools/crates/wasm-pkg-core/src/wit.rs

Lines 180 to 212 in 0d3b316

	// add deps from config first in case they're local deps and then add deps from the directory
	if let Some(overrides) = config.overrides.as_ref() {
	for (pkg, ovr) in overrides.iter() {
	let pkg: PackageRef = pkg.parse().context("Unable to parse as a package ref")?;
	let dep = match (ovr.path.as_ref(), ovr.version.as_ref()) {
	(Some(path), v) => {
	if v.is_some() {
	tracing::warn!("Ignoring version override for local package");
	}
	let path = tokio::fs::canonicalize(path)
	.await
	.with_context(|| format!("resolving local dependency {}", path.display()))?;
	Dependency::Local(path)
	}
	(None, Some(version)) => Dependency::Package(RegistryPackage {
	name: Some(pkg.clone()),
	version: version.to_owned(),
	registry: None,
	}),
	(None, None) => {
	tracing::warn!("Found override without version or path, ignoring");
	continue;
	}
	};
	tracing::debug!(dependency = %dep);
	resolver
	.add_dependency(&pkg, &dep)
	.await
	.with_context(|| format!("unable to add dependency {dep}"))?;
	}
	}
	let (_name, packages) = get_packages(path)?;

My one concern is the comment on L180 making the get_pacakges move from L212 tricky.