Adjust styling of disabled dropdowns when automodeling is in progress

[robertbrignull]

This changes the dropdowns when the automodeling process is in progress. The Dropdown component now has new features that we can make use of.

Previously, we showed a usable dropdown, except that the only available option was "Thinking...". But the user could still click on the dropdown and it was a little odd.

Now, we show a disabled dropdown that the user cannot click on. The dropdown is still showing the "Thinking..." text.

I recommend checking out the storybook to see what it looks like.

Checklist

• CHANGELOG.md has been updated to incorporate all user visible changes made by this pull request.
• Issues have been created for any UI or other user-facing changes made by this pull request.
• [Maintainers only] If this pull request makes user-facing changes that require documentation changes, open a corresponding docs pull request in the github/codeql repo and add the ready-for-doc-review label there.

[shati-patel]

🎨 ✔️