module: default to commonjs when format cannot be detected

[avivkeller]

When --experimental-detect-module is enabled, the default format will no longer be commonjs; instead, it will be null until the source is loaded. In this PR, the behavior is changed to default to commonjs, aligning with the non-experimental behavior.

[GeoffreyBooth]

@nodejs/loaders

[GeoffreyBooth]

This seems to undo part of #50314 but not necessarily incorrectly; @aduh95 can you please review?

[avivkeller]

This change, while it resolves one issue, it introduces several others (E.G. node --experimental-detect-module /xxx/test/fixtures/es-modules/package-without-type/module.js will not work now)

[avivkeller]

Marking as draft, as some things need to worked out before this is ready