qt5base: change dir/file structure for Qt5 install in staging-dirs

qt5base: change dir/file structure for Qt5 install in staging-dirs

Main objective is to make sure every Qt5 related file is clearly about
Qt version *5*. For files which do not contain the version number, make
sure the path contains it (e.g. suffixing the directory paths with
"/qt5"). This is done for host and target builds and accounts for the
following paths:
/bin -> /bin/qt5
/share -> /share/qt5
Every file inside /lib (except /lib/qt5/* which is covered by the
archdata-directory) is already versioned by its respective file names.
Keep target specific host builds inside $(STAGING_DIR)/host.