Improved logs and behavior when starting processes

[sezanzeb]

• input-remapper-reader-service waits for pipes to be created by the gui, making it possible to start the input-remapper-reader-service process first, and then the gui. If it is already running, the gui will not use pkexec to ask for a password, making it behave similar to the startup of input-remapper-service. This means Allow reader-service to be started separately #980 is no longer necessary and can be reverted
• checks if another reader-service is already running and logs a warning
• gui checks if another gui is already running and logs a warning
• wraps code in inputremapper/bin in classes, which makes writing patches in tests easier