FE: Allow users to create a Premium trial - Trial flow

Summary

In &5750 (closed) we are introducing the ability to take out a trial for Premium or Ultimate. As a result, we need to update the current trial flows to indicate which plan is being requested. The current trial flow cites the Ultimate plan in multiple places, so a new trial flow for Premium needs to be created and connected to the new Premium trial plan.

Proposal

Create a Premium version of the trial flow, connected to the Premium Trial Plan

Designs

#2729 (closed)