This removes the majority of `../../../../../../test_util` relative
imports from the codebase, allowing us to move this code more easily in
the future.
Noticed that we're checking more module paths than necessary. In
particular the module path array contains a couple of entries with a
duplicated `node_modules/node_modules` suffix.
```js
[
// ... more entries before here, where some also contain duplicate suffixes
"/Users/marvinhagemeister/dev/preact-render-to-string/node_modules/.deno/node_modules",
"/Users/marvinhagemeister/dev/preact-render-to-string/node_modules/node_modules", // <-- duplicate suffix
"/Users/marvinhagemeister/dev/preact-render-to-string/node_modules",
"/Users/marvinhagemeister/dev/node_modules",
"/Users/marvinhagemeister/node_modules",
"/Users/node_modules",
"/node_modules",
"/node_modules" // <-- duplicate entry
]
```
This was caused by a misunderstanding in how Rust's
[`Path::ends_with()`](https://doc.rust-lang.org/std/path/struct.Path.html#method.ends_with)
works. It's designed to match on whole path segments and the suffix
`/node_modules` is not that, except for the root entry. This meant that
our check for if the path already ended with `node_module` always
returned `false`. Removing the leading slash fixes that.
While we're at it, we can remove the last condition where we explicitly
added the root `/node_modules` entry since the while loop prior to that
takes care of it already.
This internal node hook is used by libraries such as `ts-node` when used
as a require hook `node -r ts-node/register`. That combination is often
used with test frameworks like `mocha` or `jasmine`.
We had a reference to `Module._preloadModules` in our code, but the
implementation was missing. While fixing this I also noticed that the
`fakeParent` module that we create internally always threw because of
the `pathDirname` check on the module id in the constructor of `Mdoule`.
So this code path was probably broken for a while.
```txt
✖ ERROR: Error: Empty filepath.
at pathDirname (ext:deno_node/01_require.js:245:11)
at new Module (ext:deno_node/01_require.js:446:15)
at Function.Module._resolveFilename (ext:deno_node/01_require.js:754:28)
at Function.resolve (ext:deno_node/01_require.js:1015:19)
```
