2071: Add an option to only start a new demo when connect while automatically record demos r=def- a=sirius1242
Origin auto demo recording of ddnet will generate lots of demo files especially when playing in mods which have shorter rounds, such as infclass. I added a new option to open a new demo file only when connect to server (include map changing), this is disabled by default, and can use `cl_auto_demo_on_connect 1` to open. It works only when `cl_auto_demo_record` open.
Co-authored-by: sirius <sirius.ustc@gmail.com>