Add contract test for suggested reviewers dropdown

What does this MR do and why?

These changes were initially merged in !100653 (merged) and were reverted in !105198 (merged) after @leipert discovered (internal - Slack) that the Pact dependencies send usage data via Google Analytics.

This MR includes the original MR, plus opting out of sending usage data. Even if it's benign, we don't want to enroll engineers and users in sending usage data without their consent.

It also removes the dependencies that were added to package.json in the original MR. They're also included spec/contracts/consumer/package.json where they won't cause conflicts. The jest:contract script added to package.json can still be used to run contract tests from the root directory, as long as the packages in spec/contracts/consumer/package.json have been installed first.

Background

Contract tests were added recently and there is ongoing work.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

doc/development/testing_guide/contract/index.md

@@ -26,6 +26,8 @@ The contracts themselves are stored in [`/spec/contracts/contracts`](https://git
 
 Before running the consumer tests, go to `spec/contracts/consumer` and run `npm install`. To run all the consumer tests, you just need to run `npm test -- /specs`. Otherwise, to run a specific spec file, replace `/specs` with the specific spec filename.
 
+You can also run tests from the root directory of the project, using the command `yarn jest:contract`.
+
 ### Run the provider tests
 
 Before running the provider tests, make sure your GDK (GitLab Development Kit) is fully set up and running. You can follow the setup instructions detailed in the [GDK repository](https://gitlab.com/gitlab-org/gitlab-development-kit/-/tree/main). To run the provider tests, you use Rake tasks that can be found in [`./lib/tasks/contracts`](https://gitlab.com/gitlab-org/gitlab/-/tree/master/lib/tasks/contracts). To get a list of all the Rake tasks related to the provider tests, run `bundle exec rake -T contracts`. For example: