Some mistakes slipped into the PR introducing the new environment in the discuss
app. This PR fixes those mistakes :
- triggers on this.env.bus that were listen on core.bus
- inconsistent service names between discuss_public_boot/main
- call to Component.env.services.messaging while messaging was available in this.env
- remaining useSubEnv in container that were not needed anymore
closesodoo/odoo#92533
Signed-off-by: Sébastien Theys (seb) <seb@odoo.com>