build: Move ModemManger logic into the shared library to respect Android
Android's project treble has linker namespaces isolation feature that prevents executables from sharing their symbols with shared libraries. This causes a lot of errors during loading plugins:
dlopen failed: cannot locate symbol "mm_broadband_modem_get_type"
referenced by "/vendor/lib64/ModemManager/libmm-plugin-thuraya.so"...
Moving all symbols into the same namespace solves the issue.