Fixes#38209
OAuth2-linked accounts that sign in via the password form were still
redirected to the provider end_session_endpoint on logout because the
redirect was keyed off account LoginType.
Store the session sign-in method (password vs oauth2) and only use
RP-initiated OIDC logout when this session was authenticated via OAuth2.
Sessions without the new key keep the previous LoginType behavior.
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Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>