implement pnpm migration (#22262)

### What does this PR do?

fixes #7157, fixes #14662

migrates pnpm-workspace.yaml data to package.json & converts
pnpm-lock.yml to bun.lock

---

### How did you verify your code works?

manually, tests and real world examples

---------

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Dylan Conway <dylan.conway567@gmail.com>

src/install/NetworkTask.zig

@@ -70,6 +70,10 @@ fn countAuth(header_builder: *HeaderBuilder, scope: *const Npm.Registry.Scope) v
     header_builder.count("npm-auth-type", "legacy");
 }
 
+const ForManifestError = OOM || error{
+    InvalidURL,
+};
+
 pub fn forManifest(
     this: *NetworkTask,
     name: string,
@@ -77,7 +81,7 @@ pub fn forManifest(
     scope: *const Npm.Registry.Scope,
     loaded_manifest: ?*const Npm.PackageManifest,
     is_optional: bool,
-) !void {
+) ForManifestError!void {
     this.url_buf = blk: {
 
         // Not all registries support scoped package names when fetching the manifest.