[playground][enhancement] help disambiguate playground experiments

[Parker-Stafford]

Right now all experiments from the playground are named playground experiment which makes it hard to do analysis on the compare experiments page.

Add timestamp and potentially a counter to experiment names so users can more easily disambiguate them

Example:

[axiomofjoy]

Rather than timestamp, we should use letters corresponding to the A, B, C, and D columns in the UI and should support setting the experiment name, description, and metadata via subscription input.

[axiomofjoy]

We probably want to add the ability for the user to specify experiment details (name, description, metadata) in the ui for each prompt. Punt until after MVP release