Refs: #1886

Adds better log out support

Adds a "system" option to follow the system locale

Trying to improve clarity that there are only a small subset of features that require an account

Removes GK auth extension dependency

Adds a limit on the number of queries

- adds headings, and moves the majority of text content to the body of each step
- most steps now have a simple, one-line description
- adds "try now" section to premium feature walkthrough with a button to try
- adds and updates content in premium feature introduction step
- removes an unnecessary file

Aligns with other gate messaging states
  Simplifies context keys for premium
Fixes purchase link to point to account site
Polishes other gate messaging

Reduces startup impact

- adds new images to premium feature sections
- fixes side bar view images to be side-by-side
- in the last step of the getting started walkthrough, add image and a button that links to the premium feature walkthrough
- updates the old settings.png image with a new version
- adds a new image of the quick setup
- adds a note about worktrees not working on the web

Adds show method to webview views

Adds Learn about Premium Features to command palette

Adds links footer to home view when welcome is hidden
Polishes welcome/settings page headers
Removes links from welcome page
Removes old welcome view