sessions: fix customization harness layer violation by using session types (#316231)

Replace the eslint-disabled import of LOCAL_SESSION_ENABLED_SETTING from
the providers layer with ISessionsManagementService.getAllSessionTypes().
The local harness is now registered when any provider offers a session
type with id 'local', and removed when it disappears.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>