Testing tool for urwid types

[Ezio-Sarthak]

We use urwid types on a general basis throughout the codebase. While our use-case is large, we don't currently have types that the respective input markups (e.g., Text) expect. It would be nice if we have runtime manual tests for different formats to support the urwid types for which support is claimed, and then we can work on suitable typing for them from that. This way, we may avoid some bugs with soup2markup/transform (HTML -> urwid rendering) by treating the data more cleanly.

CZO Previous discussion: link
Related open PR: #1101.

[zulipbot]

Hello @zulip/server-refactoring members, this issue was labeled with the "area: refactoring" label, so you may want to check it out!