remove all commands that resulted in "COMING SOON" notifications

[shouples]

Summary of Changes

Closes #283.

Instead of showing actions that we intend to include (but are blocked by sidecar updates or other dependencies), we're hiding them from the UI entirely. The comments around the associated code now also link to this PR so it should be easy to revert the when clauses in package.json once we get around to implementing the associated functionality.

The following were also blocked from showing up in the command palette and may need to be reverted once we implement them:

• confluent.kafka-clusters.item.rename
• confluent.resources.item.rename

The three confluent.schemaViewer.* commands already had a when: false section in the command palette.

Pull request checklist

Please check if your PR fulfills the following (if applicable):

Tests

• Added new
• Updated existing
• Deleted existing

Other

• Does anything in this PR need to be mentioned in the user-facing CHANGELOG or README?
• Have you validated this change locally by packaging and installing the extension .vsix file?

  gulp clicktest

[noeldevelops]

Nice!