Roll Up Autoloader to Parent Directory

# Issue

When the configure command is run on a plugin being created in a subdirectory of a larger project (e.g., put into `plugins` inside of a repo that has `wp-content` as its root), the option to use a `composer.json` file in a parent directory (e.g., `wp-content/composer.json`) does not copy the autoloader configuration to the parent Composer file. Additionally, when autoloading is hoisted to a parent context, automated tests will fail because the autoloader isn't being loaded in the plugin in a test context (rather than the plugin itself loading the autoloader file, it is assumed to be loaded already via an mu-plugins loader or similar).

# Steps to Reproduce

Create a new WordPress plugin using this repo and select the options for it to be installed in a subdirectory of a larger project and to use the parent Composer configuration, then try running unit tests and observe that they fail due to not being able to resolve classes by name and autoloader.

# Recommended Fix

When configuring a new plugin, if the option is selected to use the parent Composer configuration, copy over the `autoload` and `autoload-dev` configuration from the plugin to the parent `composer.json`. Additionally, either programmatically include a `require_once` to the autoloader in the plugin's `tests/bootstrap.php` file based on the configuration of the vendor directory in the parent `composer.json`, or prompt the user to do so themselves based on where/how they have configured the autoloader.