Split container refreshes full content when dragging to resize the split

[dweymouth]

Checklist

• I have searched the issue tracker for open issues that relate to the same problem, before opening a new one.
• This issue only relates to a single bug. I will open new issues for any other problems.

Describe the bug

Split.SetOffset refreshes everything, when it should just move/resize things. This causes lagginess with fyne_demo and the efficient run loop PR (where input events are currently processed as fast as they arrive).

Related: #5456

How to reproduce

run fyne_demo on the efficient runloop branch, resize a split container

Screenshots

No response

Example code

n/a

Fyne version

develop

Go compiler version

n/a

Operating system and version

all

Additional Information

No response

[andydotxyz]

Good point, no idea why we just shortcut the resize by calling Refresh

[dweymouth]

Fixed on develop