SW-9521 - Set composer autoloader-suffix option

This prevents unnecessary file changes caused by the generated composer
autoloader.

In the default configuration the composer autoloader classes are
generated with a random suffix.
Merge pull request #1562 in SW/shopware from feature/master/sw-9521-set-composer-autoload-suffix to master

* commit '2bfb1a7279d40d0fb8a538e5c070d6d16a7daae5':
  SW-9521 - Set composer autoloader-suffix option