Automatically add nitro module paths to be inlined

Environment

Node v20.9.0, Nitropack 2.10.4

Reproduction

https://github.com/cjpearson/nitro-externals-test

To reproduce:

• Inside nitro_module/, run yarn install && yarn unbuild
• Inside nitro_app, run yarn install && yarn dev

Describe the bug

When adding a server handler through a module, if there are relative imports within the handler, it will crash in dev mode.

For example, the following will work in the prod build but fail with [cause]: Error [ERR_MODULE_NOT_FOUND]: Cannot find module '/nitro-module/dist/runtime/utils/greeting.mjs' in dev.

import { defineEventHandler } from 'h3'
import { sayHello } from '../utils/greeting'
export default defineEventHandler((event) => {
    return sayHello()
})

This is a common issue reported with Nuxt, but is also reproducible with a pure nitro module.

https://github.com/nuxt/nuxt/issues/18909
https://github.com/nuxt/nuxt/issues/26150

There is a workaround described here, but with a large module the number of paths becomes quite large and it's easy to miss one as missing one does not guarantee a build error.

Additional context

No response

Logs

Start by reproducing the failure with the commands in nitro_module/ and nitro_app/, focusing on the server handler's relative import from ../utils/greeting. Trace how module paths are handled in dev mode versus the production build. Done means module-provided relative imports are automatically inlined and the dev server no longer raises ERR_MODULE_NOT_FOUND.