[tintinhamans]

Merge after #635.

NGMPGame::launchGame wrote the run ahead settings from the service config straight into engine globals, so only an online match could set them and every new setting needed another block there. NetworkSettings (new, in Core) now holds the per-match send and input_delay settings. ConnectionManager::init fills it from compiled defaults, and in an online match from the service config, then sets the run ahead globals from it. LAN uses the same defaults as online. Later PRs add their keys to the same struct.

The service config is now grouped (connection, send, input_delay, lobby, telemetry) and only the grouped keys are read. A key the service sets is used, a missing key keeps its compiled default, values are clamped. The flat reader, use_default_config, the retail and custom profiles and the ibra_* keys are gone, so only new clients connect. Renames include relay_all_traffic to connection.relay_only, ice_implementation to connection.ice_engine, enable_host_migration to lobby.host_migration, do_probes to telemetry.screenshot_probes and frame_grouping_frames to send.frames_per_packet. The screenshot keys move into telemetry as well: screenshot_width, screenshot_height and the screenshot_upload_bytes_per_sec and screenshot_slot_offset_ms of #635.

Compiled defaults change: lobby.host_migration false (was true), screenshot size 960 x 600 (was 557 x 333), minimum run ahead 4 (was 6). Also fixes delete instead of delete[] in FrameMetrics, which now also reallocates its FPS history when the service sets a different input_delay.fps_history_samples, so a value above the default 30 cannot overrun the buffer. No wire change.

Tested: every tip builds x86 Release z_generals.