19300: Adds un-maximize functionality to the MPV component suite.

When a panel is maximized, the un-maximize action restores the previous
panel state, unless another panel has been shown/hidden between the
maximize and un-maximize actions. In that edge case, the original panel
visibility state is restored.

Arvados-DCO-1.1-Signed-off-by: Lucas Di Pentima <lucas.dipentima@curii.com>