Improvements to Code Coverage extension

[worksofliam]

1. We need one section in the view which has the tests the user has defined.
2. We need another section which shows all the results from run coverage tests, as well as a way to import a cczip file from either the IFS or local machine.
3. With the results view, we would be able to compare two test results.

[worksofliam]

#1038

[worksofliam]

How about the test API? https://code.visualstudio.com/api/references/vscode-api#TestController

[worksofliam]

Open issue about test coverage support: microsoft/vscode#123713