Moves every stored timer from one backend to the other. First copies, second reads the copy back, and only then drops the original.
The client both extensions are loaded on.
The backend to move timers out of.
The backend to move them into.
Whether to leave the originals behind instead of dropping them.
What was moved, or null if the source could not be opened.
Moves every stored timer from one backend to the other. First copies, second reads the copy back, and only then drops the original.