Makeper_pixel_transparency enabled by default

[YeldhamDev]

The logical next step now that #91333 is merged.

Technically a compatibility break, since this changes a default project setting.

[bruvzg]

Might be worth overriding it for the editor, but I would not enable it for the projects.

Projects use embedded windows by default, so it's useless and can add unnecessary overhead.

[clayjohn]

Are popup shadows something that are worth slowing down the editor for?

[mrjustaguy]

IMO no.

[Mickeon]

Some users regard the editor as being somewhat sluggish as is, so if this is changed by default it would be nice to address the few other pain points first. We now allow V-sync to be disabled in the editor for similar reasons, I think?

[YeldhamDev]

The problem is that the default project theme has popups with shadows and rounded corners, which not just means they look wrong, but also the warning message will display for them.

[Zireael07]

@YeldhamDev: Solution: remove shadows and rounded corners from default theme.

[akien-mga]

Yeah I don't think we should enable this by default, so we should change the editor theme so that it doesn't use shadows.

As we've seen in #91333 per-pixel transparency for Nvidia on Windows is broken. That's the configuration the vast majority of Godot users has, so we can't have a default editor theme that's broken for them.

In the past we also had significant issues with per-pixel transparency on various drivers, this isn't safe to enable by default just for cosmetic reasons.

[YeldhamDev]

Yeah, I see the point. Closing it.