Appearance: Use a dynamic instead of fixed size for the text preview area.

Fixes #17872.

Appearance: Set a fixed preview text width and wrap

Larger font sizes and translations make the window too wide, grow
window vertically instead by wrapping.

Change-Id: I5850374f0fc917176927010d8e50b44033d366b1
Reviewed-on: https://review.haiku-os.org/c/haiku/+/5501
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>
Reviewed-by: Adrien Destugues <pulkomandy@pulkomandy.tk>

Appearance: Added BSpinners for setting font sizes.

Change-Id: Ic8036e512cda3e30b653092fa718b03e1b042ecc
Reviewed-on: https://review.haiku-os.org/710
Reviewed-by: Kacper Kasper <kacperkasper@gmail.com>

Embedded the Font into the Appearance Preflet

* Copied the essential parts from the Font preflet into the Appearance
preflet folder.
* Adopted these files to better direct where BMessage arrive and why.
The Font preflet just forwarded them from the BWindow handler,
which was quite messy.
* Embedded the Font preferences as another tab. The first one actually,
with the Decor settings also moved in front of the Anti-Aliasing tab.
* Refactored the Defaults and Revert button updates in the window code.
* AInclude all active settings tabs in the Defaults and Revert handling
for consistency. But eventually, the buttons should only affect the
currently visible page.

Embedded the Font into the Appearance Preflet

* Copied the essential parts from the Font preflet into the Appearance
preflet folder.
* Adopted these files to better direct where BMessage arrive and why.
The Font preflet just forwarded them from the BWindow handler,
which was quite messy.
* Embedded the Font preferences as another tab. The first one actually,
with the Decor settings also moved in front of the Anti-Aliasing tab.
* Refactored the Defaults and Revert button updates in the window code.
* AInclude all active settings tabs in the Defaults and Revert handling
for consistency. But eventually, the buttons should only affect the
currently visible page.