Drush: Convert aliases to Drush 9 syntax

[tormi]

Currently, Drush aliases doesn't work because composer.json requires "drush/drush": "^9.0.0" (Silta req.), but Drush aliases are using Drush 8 syntax.

There is a helper command for converting aliases to Drush 9 syntax: https://drushcommands.com/drush-9x/site/site:alias-convert/