Improve UX for GitLab for Jira App Setup
## Problem to solve
This epic collects all the issues related to improving the [GitLab.com for Jira Cloud](https://marketplace.atlassian.com/apps/1221011/gitlab-com-for-jira-cloud?tab=overview&hosting=cloud) application on the Atlassian Marketplace.
In collaboration with Atlassian, we identified a large number of problems with this app, which were leading to a low installation success rate and very poor reviews. Specifically:
1. Poor explanation of the target audience on the listing page (https://gitlab.com/gitlab-org/gitlab/-/issues/229542)
1. Poor documentation for how to setup in GitLab's docs (https://gitlab.com/gitlab-org/gitlab/-/issues/229355)
1. Bad UX (broadly) for the integration setup (https://gitlab.com/gitlab-org/gitlab/-/issues/13020)
1. Poor copy on error message during setup (https://gitlab.com/gitlab-org/gitlab/-/issues/13019)
1. Functionality is behind a Premium account, so we should move to Core (https://gitlab.com/gitlab-org/gitlab/-/issues/233149)
Additionally, we identified a number of UX improvements that could really polish the experience and make it easy to use.
## Proposal
Below are a number of issues which solve these problems. But broadly the plan is:
1. Improve the content, in our Docs, on the Atlassian Marketplace, and in the UI itself, to make it clear what this Application does, how it works, and how to use it
1. Improve the setup flow, making it simple and clear to add namespaces
1. Polish the look-and-feel, making it feel like an official GitLab application and part of our suite of tools
## Timeline
This work began in %13.5, and is planned to be complete by %13.10
epic