feat: new upgrade flow

[imor]

This PR:

• Improves typescript checking in VSCode by:
  • Adding deno.json file to typecheck edge function.
  • Enabling deno in .vscode/settings.json. Deno extension needs to be installed in VSCode for these changes to take effect.
  • Adding types to code wherever missing.
• Move the schema comment format from plain text to JSON format for easier parsing.
  • The code to parse the schema is backwards compatible with the plain text format.
  • This code is also exposed to clients like Supabase frontend, so have consistent parsing logic everywhere.
• The JSON comment now tracks the old and new versions to support upgrades in the Supabase UI.
• Fixed bugs in which return values from the runSQL function were interpreted incorrectly.
• The upgrade flow will just run the install function. Because the APIs used in it are idempotent, running it again upgrade to the latest version.