More typing edge cases

Seen while updating `jupyter_server`:

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

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

```python
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,
```

```python
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)""",
)
```