Fix popup windows content margins

[passivestar]

Closes #89718

This does 2 things:

• Makes AcceptDialog use margins that scale with the editor scale to support HiDPI displays

• Unifies all of the popup margins in the editor by decreasing the margins of the Project/Editor Settings popups and increasing them for AcceptDialogs, making them meet halfway at the same value

Visual comparison (default theme, 1.5 editor scale):

Before:

After:

[passivestar]

@AThousandShips this isn't macos-specific as I originally thought, this is HiDPI-specific. The linked issue just wasn't updated

[passivestar]

Increased the margin multiplier to make sure buttons align perfectly vertically when using the default base margin value. It's a bit of a magic number but it's best to change the multiplier for popups instead of the base margin value so that only popups are affected with this change

Tested this with both high and low dpi, both with custom and the default theme

[Calinou]

Tested locally, it works as expected. This looks a fair bit better to me, nice work 🙂

Default

Before	After (this PR)

Before	After (this PR)

Compact

No change. I think there should be more spacing around dialogs when in compact mode (texts can get dangerously close to the OS' rounded corners cutting them off), but this may need to be handled in its own PR.

Spacious

Before	After (this PR)

Before	After (this PR)

[passivestar]

but this may need to be handled in its own PR

Yeah tbh I've been kind of ignoring the existence of compact mode so far because iirc the plan was to first introduce those spacing presets in one PR and then make them look not broken at a later point (which never happened so compact mode now has 0px margins all over the place). By the look of it compact mode will need a big amount of work, so I'm wondering if the spacing presets will need to be re-evaluated to better understand how they fit into future plans, especially for 4.4 in case any UI/theme related changes are planned

CC @coppolaemilio @adamscott

[akien-mga]

Thanks!