Fully support ESM helpers in projects using "type": "module" in package.json

### Runtime

node.js

### Runtime version

22.5.1

### Module version

7.0.3

### Used with

hapi

### Any other relevant information

PR #146 added partial support for ESM helpers, such as those using the `.mjs` extension. However, the loader still uses `require()`, which is only allowed to load ESM under limited circumstances. Notably, if a project using `vision` has `"type": "module"` in its package.json and has helpers with a `.js` file extension, then `require()` is not allowed to load them and Node will throw an `ERR_REQUIRE_ESM` error at: https://github.com/hapijs/vision/blob/cc598dba5ac049d183138155ad15292153859623/lib/manager.js#L210

I believe the only way to fix this is to use `import()` instead of `require()`. In recent versions of Node, `import()` is available within CommonJS modules and `import()` is capable of loading both ESM and CommonJS.

Since `import()` is async, it would have to be awaited, which could be problematic for the surrounding code, as it seems to be synchronous. But in principle, this should be a simple change.

### What problem are you trying to solve?

I am unable to use helpers with ES module syntax and a `.js` file extension in a project with `"type": "modele"` in package.json.

### Do you have a new or modified API suggestion to solve the problem?

No API changes should be necessary.