Problem/Motivation
In #2465887: Extract the install/uninstall functionality to a ThemeInstaller responsibility of [un]install of themes moved to theme_installer service but no CR filed and deprecated methods still used in core
Proposed resolution
Replace all usages of ThemeHandlerInterface::uninstall() and ThemeHandlerInterface::install() and trigger a silenced error.
Remaining tasks
patch, review & commit
User interface changes
None
API changes
None
Data model changes
None