Integrate with VSCode Test Coverage capabilities

[isc-tleavitt]

See:
https://code.visualstudio.com/updates/v1_88#_test-coverage
https://code.visualstudio.com/api/extension-guides/testing#test-coverage

[gjsjohnmurray]

See also https://ideas.intersystems.com/ideas/DPI-I-437

[isc-tleavitt]

@gjsjohnmurray thanks for the links!