AboutSystem, Installer: show light/dark logos

* Use B_DOCUMENT_TEXT_COLOR and B_DOCUMENT_BACKGROUND_COLOR instead
of black on white in text views.

* Depending on HAIKU_DISTRO_COMPATIBILITY_OFFICIAL build flag, either
show the official Haiku logo or the Walter logo.

* If the official Haiku logo is used, show a version with black letters
if B_DOCUMENT_BACKGROUND_COLOR is light, and white letters if it's not.

* Remove the "installer" versions of the black-on-white Haiku logo.
Instead introduce "black|white-on-transparent" logos with a
transparent background.

* Fixed the leave shadows in logo Wonderbrush files. Especially the
yellow leave's shadow appeared too large and blurry.

Change-Id: I6d3ac384d2c96d91d35e6d6e85025c9e2064d59e
Reviewed-on: https://review.haiku-os.org/c/haiku/+/7419
Reviewed-by: waddlesplash <waddlesplash@gmail.com>

Installer: use Walter as a placeholder logo

For non-official builds, Installer had no logo. This led to a window
sizing bug which is not seen in the official builds (both nightlies and
releases) as they both use the Haiku logo there.

Use Walter as a placeholder logo in that case. The png is generated from
the wonderbrush file in the separate artwork repo.

Change-Id: Iea361d7ac0fd2bdb147318632ff198c86c4b89c2
Reviewed-on: https://review.haiku-os.org/c/haiku/+/2180
Reviewed-by: waddlesplash <waddlesplash@gmail.com>