Rollup merge of rust-lang#144315 - lolbinarycat:bootstrap-dist-package.json, r=Kobzol

bootstrap: add package.json and package-lock.json to dist tarball

this ensures that js-related tests can still be run from within such a dist tarball.

followup to rust-lang#142924

r? ```````@Kobzol```````

Author: matthiaskrgr

src/bootstrap/src/core/build_steps/dist.rs

@@ -1068,6 +1068,8 @@ impl Step for PlainSourceTarball {
             "bootstrap.example.toml",
             "configure",
             "license-metadata.json",
+            "package-lock.json",
+            "package.json",
             "x",
             "x.ps1",
             "x.py",