What is "Shield Recipe Client"?

You should look at the links provided at the bottom of the Mozilla wiki page you cite. Seems like a Firefox "system addon" under development. Those addons are installed by Mozilla, and are not user-controllable. The Shield Recipe Client purpose appears to be to give Mozilla a further means of snooping around in your browser and performing actions, such as presenting survey questions, based on the results.

Shield is a system that addresses user attrition and satisfaction in Firefox by providing a fast and powerful way for Firefox to interact with our users.

User-facing products powered by Shield include:

Shield Studies
Recruits users to participate in testing new features and ideas that help us validate product decisions. Our users tell us what to ship.

Heartbeat
Gathers feedback from users for us to better understand what users find helpful and useful.

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