Add support for using vite outside of the theme/module directory

Pushed initial implementation of the proposed solution to MR !22.

Still needs more testing, some cleanup, docs and automated test.

It adds a new `viteRoot` config option that defaults to extension directory but can be set to for example, project root. If the value starts with /, then it is resolved relative to drupal root, otherwise relative to the extension dir.
The vite root path is then used to resolve path to manifest (configured manifest path is treated as relative to vite root) and paths to assets.

For example, to use setup with vite configured in project root and dist files generated to libraries dir (web/libraries/dist) we just need to set vite root to /.. and manifest path to web/libraries/dist/.vite/manifest.json.

/vite.config.js
/web/...
/web/themes/custom/my_theme/...
/web/themes/custom/my_theme/ts/script.ts

# settings.php
$settings['vite']['viteRoot'] = '/..';
$settings['vite']['manifest'] = 'web/libraries/dist/.vite/manifest.json';
# this can also be configured on per extension/library basis in .info.yml or .libraries.yml same as other configuration options

# web/themes/custom/my_theme/my_theme.info.yml
...
vite:
  enableInAllLibraries: true

# web/themes/custom/my_theme/my_theme.libraries.yml
my_library:
  js:
    ts/script.ts: {}

Added another config option `distPath` that should be set to dist directory path relative to vite root, the same as the build.outDir in vite config. The `manifest` config option is now deprecated in favor of `distPath` since vite manifest file is always in the same location in the dist directory.

Tests currently pass locally in an actual project but fail in gitlab ci because of the symlinked module source. Will probably need to replace `realpath` usage when resolving paths to skip resolving symlinks.

Recent changes:

• removed use of realpath function and tests are now passing also in symlinked environment
• renamed distPath config option to distDir to more closely match Vite's build.outDir config option

Also updated IS to match the proposed resolution to the current approach and to add remaining tasks.

I will work on adding tests, but otherwise this should be ready for a review.

@darvanen
An example configuration with ViteJS setup in the project root for compiling assets in custom themes and modules could look like this:

composer.json
vite.config.js
web/
  index.php
  core/
  themes/
    contrib/
    custom/
  modules/
    contrib/
    custom/
      my_module/
        my_module.info.yml
        my_module.libraries.yml
        assets/
          my_module.css
          my_module.js
  libraries/
    dist/
      .vite/manifest.json
      assets/
        my_module-G0XxVM1l.css
        my_module-BbupU5xU.js
        ...

Configure ViteJS
In vite.config.js:

import { globSync } from "tinyglobby";
import { defineConfig } from "vite";

const entrypoints = [
  // Scan all .js files in custom themes and modules.
  "./web/{themes,modules}/custom/**/*.js",
  // Scan all .css files in custom themes and modules.
  "./web/{themes,modules}/custom/**/*.css",
];

export default defineConfig({
  build: {
    // Generate asset manifest.
    manifest: true,
    // Save compiled assets and asset manifest to the web/libraries/dist/ directory.
    outDir: 'web/libraries/dist',
    // Configure entrypoints.
    rollupOptions: {
      input: globSync(entrypoints),
    },
  },
  ...
});

Configure custom themes/modules
In theme/module.info.yml:

...
vite:
  // Set vite root to the parent directory of Drupal web root directory.
  viteRoot: '/..'
  // Set vite dist directory same as outDir option in vite config (it is resolved relative to viteRoot).
  distDir: web/libraries/dist
  // Enable vite support for all libraries and components.
  enableInAllLibraries: true
  enableInAllComponents: true

In theme/module.libraries.yml:

// Provide relative asset paths as normally, Vite module will automatically make them relative to viteRoot and depending on mode prepend vite dev server url or rewrite them based on asset manifest.
my_library:
  css:
    theme:
      assets/my_module.css: {}
  js:
    assets/my_module.js: {}

How Vite module works
In this example, the Vite module will:

- check if my_module/my_library library should be managed by vite module
- for each asset in library
  - trasform asset path (based on configured viteRoot and drupal web root) so it is relative to vite root
  - in dev mode:
    - prepend dev server url to the transformed path
  - in dist mode:
    - match transformed source path to the dist path based on vite asset manifest
    - transform dist path so that it is relative to the module directory

@reinfate
Tests and fix for @vite/client look good. Thanks.

Reverted the last commit that broke the functionality and pushed small fixes for issues reported by phpstan.

I'm already using changes from the MR on a few work projects, and it works fine.
Since reinfate and mh_nichts also reported that the changes work for them, I think we can merge this.

And maybe as a follow-up in a separate issue, work on adding some examples to the docs to make it easier to start using functionality added in this issue and the module in general.

Merged and released in 1.5.0.