stream settings: Show stream header in narrow view.
stream settings: Show stream header in narrow view.

This changes the streams overlay so that the header with the stream name or
with 'Create stream' is also visible in a narrow window.

Resolves #22963

zulip/zulip,zulip/zulip,zulip/zulip,zulip/zulip,zulip/zulip,zulip/zulip,zulip/zulip