Allow control of merged coverage results behaviour

As per https://developercommunity.visualstudio.com/t/running-multiple-test-assemblies-at-the-same-time/1688096

@MarcoRossignoli

For the moment, we don’t offer a way to disable the merging. Can you open an issue on https://github.com/microsoft/vstest/issues so we can collect the community interest on this feature and prioritize it? Can you also explain, if possible, what’s your scenario and the reason not to have a merged global report?

Steps to reproduce

Create two test projects each with runsettings specifying different results directories and run tests at the same time.

Expected behavior

Separate results

Actual behavior

There is only a single merged results.

Scenario

Currently I am a contributor to a code coverage vs extension that is triggered by the test explorer and will create individual cobertura files for each project ( by running OpenCover or Coverlet for each test project ) that can be viewed by the developer if required. These cobertura files are then used to create a single merged html report.
The extension will shortly permit using Ms code coverage over the existing tools.

So ultimately a merged report is what I require but for consistency I would like the individual results given that vstest has access to them.