gn2bp: Update desc.json and Android.bp with is_build_cronet=true

is_build_cronet=true is required by aosp/2384115
This CL also updates gen_desc_json.sh to set is_build_cronet=true

Test: gen_desc_json.sh, update_results.sh
Change-Id: I057a7b9d4bb2038f430c1dbc59de72ba18bdf93c
6 files changed