Add support for using vite from the root of the project

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';

# 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 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.