Add explicit moc includes to sources for moc-covered headers

• speeds up incremental builds as changes to a header will not always need the full mocs_compilation.cpp for all the target's headers rebuild, while having a moc file sourced into a source file only adds minor extra costs, due to small own code and the used headers usually already covered by the source file, being for the same class/struct [etc]

See https://frinring.wordpress.com/2023/06/28/include-also-moc-files-of-headers/ and frameworks/kirigami!1127 (merged) for more.