Remember stacksize override for inserters when disabled

[mrvn]

TL;DR

Toggling the stacksize override checkmark should remember the last value.

What?

Turning the stacksize override off and on resets the value to the maximum stacksize. Instead remember the last value, at least as long as the inserter GUI is open.

Why?

Sometimes you just need to re-sync an inserter so it starts picking up items at the right time or have it clear a backlog of items quickly and then go back to stacksize limited mode.