Backport CI changes, bump Gluon to v2021.1.2+, update batman-adv to v2023.3+
This is in preparation for a v0.15.3 release and contains the following changes:
- Backports CI changes from the master branch as much as possible
- updates Gluon to v2021.1.2-16-g36b8adb675ac, in preparation for:
- modules: update batman-adv to v2023.3 + multicast patches
All this is mainly done so that nodes which do not receive updates to newer Gluon/OpenWrt releases anymore due to a too small flash or RAM won't block newer nodes from activating new batman-adv multicast features.
Signed-off-by: Linus Lüssing linus.luessing@c0d3.blue