Fix clamping logic in EditorSpinSlider

[Alex2782]

... when arrow keys are pressed up or down.

Fixes #81272

I have only tried Inspertor, I am not sure if the old changes are necessary for something else.
The old version changed the values by 0.001 from time to time.

Screen-2023-09-03-200319.mp4

[MewPurPur]

I already did this in #80551. I think I did it better; I have a few doubts about how it's implemented here but I'll have to test them out.

[Alex2782]

ok, I would also like to catch mouse wheel events. e.g. Ctrl + up/down does not work under MacOS, already assigned with the system function Show all windows of the front app. But mainly to increase the usability, if it is possible directly when the mouse is over the input field, without 'input focus'.

Should I wait until 'merge' has been executed? #80551

[MewPurPur]

Would suggest against it. Would lead to a lot of accidental value changes when one tries to adjust their inspector view.

[MewPurPur]

Nevermind, this PR works well in all situations, I think it's better than mine actually. So my PR can be closed, though I think my comments can be carried over to improve the clarity of the code.

// Modifiers based on web browsers' DevTools. before the Ctrl/Alt/Shift modifier code.

// If the step is smaller than 1 but can be expressed as a 1/int fraction, then set the change to 1.
// For example, 0.001 is 1/1000, so then the change will be 1.
// Otherwise, for example if the step is 0.4, use that step directly. before the step declaration.

[akien-mga]

Thanks!