Dependency on Magento was sneaked in as part of the Computed Resolver work

This package has no declared composer dependencies on Magento, yet in https://github.com/magento/upward-php/commit/6d25b499134ceb4b4046ab996b8652e008c854f0 a dependency is hardcoded.

This means that it cannot be considered anymore as a standalone implementation of upward in PHP.

Following Dependency Inversion principle we should create an interface which `\Magento\UpwardConnector\Model\ComputedPool` implements, or make `\Magento\UpwardConnector\Model\ComputedPool` part of the `magento/upward-php` together with `\Magento\UpwardConnector\Api\ComputedInterface`.

Start by reviewing the Computed Resolver change in commit 6d25b499134ceb4b4046ab996b8652e008c854f and inspect Magento\UpwardConnector\Model\ComputedPool and Magento\UpwardConnector\Api\ComputedInterface. Determine whether the interface should be introduced in the standalone package or whether the Magento implementation belongs there. Done means the package no longer hardcodes a Magento dependency while preserving the computed resolver contract.

Written by the indexing model from the issue text.