feat: unit-test-runner 3.0 with optional coverage report handling

[NathanWalker]

PR Checklist

• The PR title follows our guidelines: https://github.com/NativeScript/NativeScript/blob/master/CONTRIBUTING.md#commit-messages.
• There is an issue for the bug/feature this PR is for. To avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it.
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What is the current behavior?

ns test init prepares app for 2.0 unit-test-runner.

What is the new behavior?

ns test init now prepares app for 3.0 unit-test-runner which is vastly improved and now includes optional code coverage reporting via convenient --env.codeCoverage flag.