[EXPLORER] Add tooltip for show desktop button (#7483)

CORE-15369

[EXPLORER] Improve appearance of Show Desktop button (#5744)

While functional, Katayama's show desktop button left much to be desired
in the realm of appearances. This commit brings improvements for

[EXPLORER] Improve appearance of Show Desktop button (#5744)

While functional, Katayama's show desktop button left much to be desired
in the realm of appearances. This commit brings improvements for it:

- When using the classic theme, the Show Desktop button now appears
more faithful to its Microsoft counterpart, emblazoned with an icon,
and encased in a border only when hovered or pressed.
- With a visual style applied, the button behaves in one of two ways:
- If present, the Show Desktop button now properly uses the relevant
information from the visual style, just like on Windows 7.
- Otherwise, the Show Desktop button uses an icon akin to when the
classic theme is used, but with the button background's appearance
repurposed from the taskbar toolbar buttons, which are guaranteed to
exist in any Windows XP or Vista visual style you can find out there.

ReactOS's own Lautus and Mizu visual styles will be updated in the
following commits to utilize these features, while Lunar and Modern visual
styles left untouched to display Show Desktop button with icon instead.

CORE-15369

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