Replaces the existing ESM loader for dealing with external module
imports. This loader was introduced by Aspect for AIO `.mjs` scripts.
The loader will be used as foundation for a more extensive loader
that also properly handles first-party packages.
Additionally another loader is added, all packed as a single
loader because our current NodeJS version only supports a single
loader per node invocation. So we implement chaining ourselves.
The new loader will attempt rewriting `.js` extensions to `.mjs`,
also it will add `.mjs` if not already done. This is necessary
in the transition phase because we don't/cannot use explicit `.mts`
extensions and also we don't specify extensions in imports yet.
Long-term we would likely use `.mts` and explicit import extensions,
but it's not yet clear how we would sync this into g3 too.
PR Close#48521
