feat: Open MR changes

• Draft: Open MR Changes (!152 - closed)
• Part 1: feat: Show icons for files in Merge Request cha... (!153 - merged)
• Part 2: feat: Open MR changes (!154 - merged)

Description

• Adds command to compare with MR base. Also adds VSCode UI contributions for this command.
• When first loaded, opens top 20 changes on Web IDE open.
• Part of this issue.

Screenshots

20230316_demo

How to test?

(Copied from !153 (merged))

1. Start local gdk and find/create a MR with a reasonable amount of changes.
2. (Optional) Setup an "Access Token" for a user
3. Start the gitlab-web-ide example app with yarn start:example
4. Visit http://localhost:8000?mrId=MR_IID where MR_ID should be the iid of the Merge Request you want to open (found in the URL of the Merge Request).
5. Enter the relevant GitLab URL and Project Path. Keep Git Ref blank.
6. (Optional) Check the I have a non-production GitLab Token and enter the "Access Token" for the user
7. Press Start GitLab Web IDE

NOTE: Make sure you have disabled cache in the network tab!