Enable UI color customization via an extension. This patch doesn't
include any UI changes as that needs to be discussed with the community
first (ticket: https://bugs.documentfoundation.org/show_bug.cgi?id=163620)
Part 1.0 (this change) is responsible for loading all the ThemeColors
from the registry into a `static ThemeColors` object, which then is
accessed in various VCL_PLUGINS as a source for the application colors.
The user now has to go to the registry (expert configuration), and
enable the theme by setting "LibreofficeTheme" to "true". It can also be
enabled via an extension (demonstrated in the Theme Template).
`testGetViewRenderState` changes to "Dark" scheme which is not present.
Changes in this patch don't allow that and use 'Automatic' as the
fallback. This caused the unit test to fail. So the test was changed to
have "Dark" scheme before changing to it.
Theme Template: https://github.com/printfdebugging/libreoffice-theme-template
Project Report: https://printfdebugging.in/libreoffice/01-themes-gsoc-2024/
Change-Id: I5193d4d34fcd2f4c5d6f124a871bd5c7f14e95a7
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/168016
Tested-by: Jenkins
Reviewed-by: Heiko Tietze <heiko.tietze@documentfoundation.org>
4bdb421440