Expand out-of-box support for UI tests

[dremin]

Summary

The goal of this PR is to fix things up and make it possible to include UI tests in the future.

• Updated flex-ui mock to support template strings and mocked additional items
• Support TypeScript, linting, and prettier within test files
  • Accomplished by including test files within tsconfig and eslint config, while instructing webpack to use an extended tsconfig that excludes the test files
• Moved jest config out of the package.json
• Fixed jest and babel config to support UI testing
• Fixed dependencies to support UI testing

Checklist

• [x] Tested changes end to end
• [x] Requested one or more reviewers

[github-actions[bot]]

0 ESLint error(s) and 0 ESLint warning(s) found in pull request changed files. :white_check_mark: No issues found!

[dremin]

Looks good. I noticed we are missing mocks for ConversationsClient and VoiceClient in flex-ui. Just wanted to call this out.

Thanks! Yeah, the mock changes aren't intended to be exhaustive, rather mostly to get things to a point where we can run UI tests. I anticipate we will be adding these mocks as tests are added.