CMake >= 3.0 supports bracket comments, and the reStructuredText
integration code in sphinx/ext/ecm.py already supports extracting
the docs from a bracket comment instead.
Editing documentation without leading line comment markers is more simple,
e,g. when reflowing text over lines.

With ECM meanwhile requiring CMake 3.5 now it is possible to switch
(and thus follow also the approach used by cmake itself).

NO_CHANGELOG

We need this to pass the --release option for binary factory release
builds.

An alternative approach would be to set that here automatically depending
on the CMake build type. Since that however ends up producing unsigned and
thus not immediately usable APKs (or would need a whole set of extra
arguments for proper signing) I'm not sure whether that's most convenient
for local use.

This is no longer needed now that the metadata happens as part of the
build process rather than afterwards on the signing system. This allows
us to simplify the code here a bit.

Those occur for example in Marble.

This adds support for image assets not represented in the appstream data,
such as the banner image for the F-Droid app, and it allows to override
appstream screenshots by local ones. The latter is e.g. used by KTrip
which provides Android-specific screenshots that way.

This should improve the alignment issues currently seen in bullet point
lists that we use frequently in the description text.

BUG: 424392

This makes use of the CMake 3.19 DEFER command to list all MODULE
targets after processing the toplevel CMakeLists. This allows us to
collect required dependencies of all plugins without changes to the
application. For example, this will fix Okular not including Poppler
because it is only linked from the plugin, thus not being able to
actually read PDFs.