package/qt5: bump packages to latest kde submodule versions

This points all qt5 packages to the latest kde submodule versions
available at https://invent.kde.org/qt/qt/qt5/-/tree/kde/5.15



There is no 5.15.8 release of the kde-maintained modules, no release
tarballs and no tags. Instead, there's just a rolling maintenance
branch. We take a snapshot of that branch and call it 5.15.8, to match
the latest qt5webengine release.

We need to remove some patches applied upstream already.

qt5location has mapboxgl as a submodule, which is not included in the
gitlab-generated tarball. Therefore, use the git download method with
submodules enabled.

We need to pin qt5 packages not available in the new upstream to the
previous 5.15.2 version.

We need to set SYNC_QT_HEADERS for all qt5 packages in the new
upstream as headers are only copied in release archives which are
not provided in the kde upstream.

Instead of calling syncqt.pl, update the MODULE_VERSION in .qmake.conf
to 5.15.8 and create a .git file so to trigger headers sync during
configure.

Hold back updating qt5webengine for now since the latest version
requires significant changes to build, just tweak existing version
to be compatible with latest kde versions for now.

Signed-off-by: James Hilliard <james.hilliard1@gmail.com>
Reviewed-by: Adam Duskett <aduskett@gmail.com>
Tested-by: Adam Duskett <aduskett@gmail.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>