Enhance netsim daemon --rssi flag handling - Allow multiple --rssi flags for different PhyKinds. - Change value format to PHY_KIND:RSSI_VALUE for clarity. - Fail fast on invalid --rssi argument format. Bug: 396160036 Test: scripts/build_tools.py --task configure compile runtest Test: objs/netsimd --rssi=ble:-20 --rssi bt_classic:-30 Test: (panic on invalid format) objs/netsimd --rssi=ble=-20 --rssi bt_classic=-30 Change-Id: I3d1563f4c1816e93b40afbd2dcd670914a8e6cbd