Stanisław

### Problem There is a need to inform a user about an action status (process ended/quit). ### Proposal - Show in-app notification when process successfully closed/quit. - Show in-app notification...

`permission_error_infobar` appears when there is an error during reading some of process files. It is too striking and intrusive and implies that Monitor is malfunctioning, which is not the case....

`CPUTreeView` must be rewritten to conform to GTK4 requirements. This will remove deprecation warnings during compilation. Also can be renamed to ProcessTreeView.

I don't think that seeing opened files by a process is useful. It is also not very resource efficient. Instead we can show a number of files that a process...