Enable eslint rule to disallow awaiting a non-thenable type

[robertbrignull]

Enables https://github.com/typescript-eslint/typescript-eslint/blob/main/packages/eslint-plugin/docs/rules/await-thenable.md

I spotted that VS Code is giving suggestions for this error in the editor but not in CI. I guess it's not included in @typescript-eslint/recommended. Enabling this eslint rule means we can fix this case and avoid introducing more in the future.

I think this fix in extension.ts is a change of behaviour, because the void operator evaluates the expression and then throws away the result and returns undefined. So previously the chosenAction === installActionName condition was always false.

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.

[aeisenberg]

Interesting. I guess it was never possible to install the cli from this code path. I never tried this out, though so I don't really know.

Thanks for catching this.

[robertbrignull]

Oh and the CI found more cases which didn't show up locally for whatever reason. I'll look into them tomorrow.

[robertbrignull]

I've pushed more linting fixes. I believe all these extra changes are behaviour preserving.

[robertbrignull]

Ok, third time's the charm. Had to tix another alert that had been introduced on main since I opened this PR.