module: add support for `nodeEntryPointConfig.loaders` in `package.json`

Currently, starting a .mjs or .cjs file allow to skip the lookup and the parsing of a package.json file, I'm reluctant to change that but I'm curious what others think.

I had to make the default resolve function sync – but we don't use anything async inside anyway, I assume it's fine. If we move the loaders off-thread (or even to make the loading of loaders itself go through non-default loaders), we might need to think of an async way of resolving those loaders, not sure.

Opening as draft because it's just at the PoC stage, and I would like to get some feedback on the initial implementation before going further.

/cc @nodejs/loaders