WIP: Setup mock server for integration specs and development

• POC MR
• Step 1 - Remove IDE singleton store
• Step 2 - Defer IDE gql client creation
• Step 3 - Setup testURL in jest jsdom
• Step 4 - Setup mock server for IDE integration spec
• Step 5 - Add integration spec "user commits changes"

DO NOT MERGE

This MR will be split up soon. Stay tuned! 😄