Rename product, namespaces, libraries, paths, and assets from Orion/orion
to Onion/onion across the tree. TCP stack-shutdown magic is now ONIO
(0x4F4E494F) to match the corrected branding.
Remove the .plugin package format and rename the stack to payload-only:
liborion_plugin → liborion_payload, IPC LAUNCH_PAYLOAD, UI payloads.xml,
and bootstrapper/util/shellui load paths under .../payloads/*.elf.
Delete dead package header validation, make_plugin_app staging, and
plugin-named lists/handlers; keep Sony Settings.Plugins resource namespace
and system_settings plugin= attributes (platform, not our format).
Hexwell