MWTransclusionDialog: Blur active input when switching modes

When show/hide options is clicked, the inputs in the main pane
move as the outline transitions in or out. This causes any dropdowns
below these inputs to become mispositioned: they don't move
because they're in an overlay.

To work around this problem, blur the active input when show/hide
options is clicked, so any dropdown attached to it is closed.
I tried blurring and immediately refocusing the active input to
force the dropdown to reposition itself, but that looks awkward
because of the transition (we'd have to wait for the transition
to complete before repositioning it, and during the transition
it'll stay open in the wrong place).

Bug: 72789
Change-Id: Ibd963690573af905066839f7276077089fa893c6
Merge "MWTransclusionDialog: Blur active input when switching modes"