Switch to xdg-terminal-exec

Solves the issue from ae10133b5e the right
way using the actual xdg-terminal-exec package and provides resillient
fallbacks no matter what the user might do.

This also removes the need to restart after changing terminals at all.

fixes #2198
fixes #2329
fixes #2673
fixes #1754

applications/Alacritty.desktop

@@ -0,0 +1,21 @@
+[Desktop Entry]
+Type=Application
+TryExec=alacritty
+Exec=alacritty
+Icon=Alacritty
+Terminal=false
+Categories=System;TerminalEmulator;
+Name=Alacritty
+GenericName=Terminal
+Comment=A fast, cross-platform, OpenGL terminal emulator
+StartupNotify=true
+StartupWMClass=Alacritty
+Actions=New;
+X-TerminalArgExec=-e
+X-TerminalArgAppId=--class=
+X-TerminalArgTitle=--title=
+X-TerminalArgDir=--working-directory=
+
+[Desktop Action New]
+Name=New Terminal
+Exec=alacritty