plugins/eis: [xwayland] Add per apps allowance and show a prompt

With the current state the user is not able to make an informed decision. Either they will get a prompt from the portal that doesnt tell them any info which process wants to send emulated input or they can blanket approve any app. We can improve on that by showing a prompt when the eis connection is established, xwayland sets the name of the eis client to the requesting process. To facilitate this we now always make xwayland connect directly to a socket and never tell it to go through the portal. When an eis_client tries to connect a dialog is shown through a helper which includes an option to remember the allowance for this client. The option can be revoked in the xwayland kcm. Since xwayland now always connects directly changing the relevant settings does now not require a restart anymore.