Appearance: Make ColorPreview size font sensitive

AddGlue to separate color preview and color control instead
of growing the preview.

Change-Id: I6a21377cebc94a6f67c5528ba02d573f146a9b4c
Reviewed-on: https://review.haiku-os.org/c/haiku/+/5500
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>
Reviewed-by: Adrien Destugues <pulkomandy@pulkomandy.tk>

PVS V568: strange uses of sizeof

Change-Id: I4c4e0395f579cf3b5ec4db2c30bbe2dc2d866de7
Reviewed-on: https://review.haiku-os.org/c/1608
Reviewed-by: Stephan Aßmus <superstippi@gmx.de>

Appearance Prefs: drag and drop between ColorWhichItems

Fixes final piece of #8618

Already added support for list items to drag colors out and you can
drag and drop between the list items and preview. but, what was
missing was drag and drop between list items. Updated
ColorWhichListItem to also accept color drops through their
parent ColorWhichListView.

Also included some related style fixes, use B_RGB_COLOR_TYPE
constant in place of (type_code)'RGBC'. 80-char limit fixes.

Simplify similar code in ColorPreview class to parse out rgb_color
from message.

ColorPreview passes dropped color along to APRView

APRView no longer accepts color drops, this is handled by ListView
and ColorPreview now.

Consolidated "RGBColor" and "which" message name strings into
constants defined in defs.h.

Change-Id: I88ec2a4ffe077620ec4cc3b032196cbff0f09615

Appearance: Use BString::SetToFormat instead of sprintf to create hex color.

Fixes a GCC7 Werror about (potential) format overflow.

Drag and drop color from Appearance ColorPreview

You can drag a color square from the color preview and drop it
anywhere that accepts a color drop.

This allows you to use the color drop feature more readily
for example to change the desktop background color or change the
color of Deskcalc.

Also did some refactoring of ColorPreview class. Make it a BControl
which eliminates the enabled bool and invoker which both are handled
by the inherited BControl class.

Did some refactoring.
* Renamed a couple of class variables following convention
* Also renamed a couple of method parameters for the same reason

Don't call Draw() directly, this is frowned upon, instead use
Invalidate() so app server can draw at the appropriate time.

Fix color preview drawing bug in Appearance. Fixes #9501

Also updated to use color constants intead of hardcoding colors. This draws a
nice 3d-ish bevelled border around the color preview box.

Rename ColorWell to ColorPreview in Appearance prefs.

No functional change intended.

I'd like to use the name "ColorWell" for a different type of
class eventually so I'm making room for it. ColorPreview is
arguably a better name for the class anyway.

Also did a style cleanup of the ColorWell => ColorPreview class at
the same time.

Fix color preview drawing bug in Appearance. Fixes #9501

Also updated to use color constants intead of hardcoding colors. This draws a
nice 3d-ish bevelled border around the color preview box.

Rename ColorWell to ColorPreview in Appearance prefs.

No functional change intended.

I'd like to use the name "ColorWell" for a different type of
class eventually so I'm making room for it. ColorPreview is
arguably a better name for the class anyway.

Also did a style cleanup of the ColorWell => ColorPreview class at
the same time.