Fixed width for time label

[minamouse]

Summary

Creates a fixed width for the time label based on the total time duration string (plus a buffer width).
Previously, as the current time string was updated, the entire player bar would shift slightly. This creates a fixed width so the other icons don't move.

Test plan

Load a file and press play.

Before:

before.mov

After

after.mov

[FelipeDefensor]

Thanks! This has bothered me for the longest time, but not quite enough so I would do something about it.

The fix would have been good, but this is already contained in #539, which changes the label to an editable input.

I am closing this.