More typing edge cases

从 jupyter_server/serverapp.py、jupyter_server/auth/identity.py 和 jupyter_server/gateway/gateway_client.py 中报告的类型检查错误开始，然后检查相关的类型声明。复现报告这些位置的类型检查，并追踪 authorizer_class、login_handler_class 和 gateway_token_renewer_class 的类型定义方式。完成标准是：在不抑制有效检查的情况下解决列出的错误。

Seen while updating jupyter_server:

jupyter_server/serverapp.py:1982: error: "object" not callable  [operator]
            self.authorizer = self.authorizer_class(

self.authorizer = self.authorizer_class(
            parent=self, log=self.log, identity_provider=self.identity_provider
        )

authorizer_class = Type(
        default_value=AllowAllAuthorizer,
        klass=Authorizer,
        config=True,
        help=_i18n("The authorizer class to use."),
    )

jupyter_server/auth/identity.py: note: In member "validate_security" of class "LegacyIdentityProvider":
jupyter_server/auth/identity.py:735: error: "RequestHandler" has no attribute "validate_security"  [attr-defined]
            return self.login_handler_class.validate_security(app, ssl_options)

    login_handler_class = Type(
        default_value="jupyter_server.auth.login.LoginFormHandler",
        klass=web.RequestHandler,
        config=True,
        help=_i18n("The login handler class to use, if any."),
    )

jupyter_server/gateway/gateway_client.py: note: In class "GatewayClient":
jupyter_server/gateway/gateway_client.py:465: error: Only concrete class can be given where
"type[GatewayTokenRenewerBase]" is expected  [type-abstract]
            klass=GatewayTokenRenewerBase,

    gateway_token_renewer_class = Type(
        klass=GatewayTokenRenewerBase,  # type:ignore[type-abstract]
        config=True,
        help="""The class to use for Gateway token renewal. (JUPYTER_GATEWAY_TOKEN_RENEWER_CLASS env var)""",
    )