Modules with the same name as a theme can not be installed anymore and vice versa

Prior to Drupal 10.2.0, it was possible to install a module with the exact same machine name as an already installed theme. Similarly, it was possible to install a theme with the name of an already installed module. No error was thrown, but this name collision could lead to hooks being called in only one of the two extensions with the same name.

The ModuleInstaller and ThemeInstaller now check if there is a theme or module, respectively, with this name already installed. If so, they throw an ExtensionNameReservedException and thereby cancel the module/theme installation.