Fix timing point changes not applying after selecting another one

[frenzibyte]

• Closes Timing point changes applying to newly-selected timing point rather than original #26581

This is resolved by scheduling the switch in control point selection, since, at the moment that the user clicks and RowBackground handles the click (returning true in OnClick), focus lost event is rolled out to any focused text box and commit calls are made.

In master, control points are switched before the focus lost event is dispatched, causing the text box to commit to the new control point rather than the previously selected one.

By scheduling, focus lost events are dispatched first, then the control point is switched in the next frame.

Before:

CleanShot.2024-01-17.at.08.41.40.mp4

After:

CleanShot.2024-01-17.at.08.39.33.mp4