Add appropriate error message when pasting inputs fails

[Perdu]

(Following discussion on Discord, mostly for tracking. I might do it sometime later)

Pasting inputs into the input editor can fail for various reasons (for instance, trying to paste inputs prior to current frame with no earlier savestate existing). Currently, pasting fails silently, and user is left to guess at what happened. It would be nice to have proper error message explaining for what reason pasting failed.

[clementgallet]

Yeah, feedback is missing in a lot of cases. I'm generally against alert windows, but we could use the status bar at the bottom of the window to indicate the reason. Moreover, there is already some code for highlighting cells/rows, so we could highlight the paste rows in red, to indicate that the operation was processed but did not reach the end.