Improved theming for Up/Down controls

[niksedk]

I've tried to make new NumericUpDown controls for better theming:

The new controls have mouse over/down color change.
The existing arrow up/down keys should still work.

Give it a test and let me know if it works: https://github.com/SubtitleEdit/subtitleedit/releases/download/3.6.13/SubtitleEditBeta.zip

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The current version looks like this with dark theme:

[jmaraujouy]

Nice job, @niksedk! This was one of the things I proposed in my #7072 "DarkTheme UI refresh?" topic.

In my opinion, now it is looking much better. 👍🏻

Thanks!

[jmaraujouy]

@niksedk

Have you noticed that, when you start SE, the up/down controls looks vertically stretched, but when you hover over them, they reset to their expected position/size?

Here's an example of what I mean:

[niksedk]

Yeah, hopefully fixed here: https://github.com/SubtitleEdit/subtitleedit/releases/download/3.6.13/SubtitleEditBeta.zip

Also, any hint on the triangle layout? Shallow not filled? Smaller?

[jmaraujouy]

It's fixed now. Thank you, Nikolaj. 👍🏻👍🏻

About the triangle up/down icons, I like the Windows 11 style. They are a little smaller, and a little bit rounder.
EDIT: Sorry. I misread your first post; I thought the new buttons were actual images. So, probably what I proposed cannot be achieved.