UX/UI: Present the Web Scraper extractor template field as a DDL

[janaka]

At present the user needs to look up the template name in docs and copy-paste. This is obviously error prone and a poor experience.

Switch to present the available templates as a DDL in the Space config UI.

Add an input field type to ConfigKey and use this to drive the UI rendering logic needed dynamically.

It might be a good idea to define input field type as an enum.