Qt/Stylesheets: allow to use native styles

[Megamouse]

• Allows the selection of all the available native system styles.
• In windows, the default style is windowsvista and is basically the same as "None". It is always bright.
  The other styles work with both bright and dark mode (I don't know about other OS).
• Fixes Use fusion QT style instead of legacy windowsvista style when not applying custom theme #14762

[hrzhu]

This commit makes the dault(bright) theme looks more primitive (and ugly) on Linux.
before:

after:

Personally I'm using a custom build with this commit reverted for now.

[Darkhost1999]

Do you mean the scrollbars and the below file, manage, etc line?

Side comment: Is there a way to make the native fusion theme and the others have colored logs?

[Megamouse]

This commit makes the dault(bright) theme looks more primitive (and ugly) on Linux. before:
Personally I'm using a custom build with this commit reverted for now.

Try #14924

[Megamouse]

Side comment: Is there a way to make the native fusion theme and the others have colored logs?

No, Not unless you wish to maintain a set of 2 additional stylesheets per native style that are slapped on top of the native style.