Existing files are not overwritten when directory is copied with CopyFromPackage

[mnocon]

Hi!

I believe there's an issue with how copy-from-package works in recipes when directory is copied.

Given following recipe:

{
      "copy-from-package": {
        "testSourceDir/": "testTargetDir/",
      }
}

Once files exist in testTargetDir they will never be updated, even when --force is used when running recipes.

The behaviour I'd expect is as follows:

1. When running composer symfony:recipes:install <package> without --force the files are not overwritten (their state is not updated).
2. When running composer symfony:recipes:install <package> with --force the files are overwritten (their state is updated).

I believe this behaviour (overwriting existing files when force is used) is consistent with what's written here: https://symfony.com/doc/current/setup/upgrade_major.html#updating-recipes

Instead, the updates process re-installs the latest version of the recipe which means that your custom code will be overridden completely. After updating a recipe, you need to carefully choose which changes you want, and undo the rest.

I've created a PR here: #756