This commit achieves two things:
1. Changes the UI of the "Create stream" form to make the
textarea previously used to get the stream description
a simple input field of type text (to suggest a single
line description).
2. Adds an extra check on the frontend side to make sure that
when users create a new stream via. the "Create stream"
option in the settings panel, they can't enter any newline
characters (i.e. we disallow the enter key from being
registered when typing out the stream description).
We must also make sure that they cannot copy-and-paste over
descriptions containing newline characters.
resolves#11617
The `tr` block does clones the `options` array (which contains the
entire subscriptions data set) very inefficiently, which leads to the
rendering being very slow.
We don't need a `tr` block here, as there is no dynamic content that
needs to be replaced.