Add CMake variable to rename kwin binaries

A CMake variable is used to specify the name of the binary.
By default this is "kwin" but building for PA changes the
name to "kwinactive". The variable adjusts all names, e.g.
kwinnvidiahack becomes kwinactivenvidiahack.

The remaining usage of kwinrc in core and libs is replaced
by a cmakedefine for the configuration name and all data
installations are moved to the defined name. Dynamic loading
for scripts & co is adjusted for loading based on defined name.

This change allows the side-by-side installation of both kwin
for desktop and kwin for Plasma Desktop without the known
issues like conflicts in config files or missing build options
if kwin desktop is used for Plasma Active.

Likewise the KCMs are not adjusted as they are not intended to
be used for kwinactive.

REVIEW: 104299
BUG: 296084
FIXED-IN: 4.9.0
CCMAIL: active@kde.org