Update and simplify gitlab-ci
- change default LCG to 103
- run build and test in one job
- test centos7 and el9
- use LCG 102b x86_64-centos7-gcc11-opt as minimum version
- add test with AIDA turned off
- small workaround for a warning originating in a Boost header
Note that this puts implicit minimum requirements to C++17 standard and to CMake 3.20.0