Support for TRX output

I'm interested in getting support for converting go test json output to TRX for easier integration with Azure Devops and other processes that already process Visual Studio-style test results. I'd be interested in contributing that feature to this project if you think it would belong here. Otherwise I would build a new engine and just pull in the testjson package from this module. I think that work would have a lot of duplication of the nice wrappers for running go tests you already have in this module.

If you think adding TRX support here would be appropriate, can you suggest the proper type of refactoring? I am a Golang newbie but eager to learn and dig in.

Read the testjson package and the existing wrappers for running go tests to understand the current output flow and where another formatter could fit. The requested outcome is TRX output from go test JSON for Azure DevOps and other Visual Studio-style result consumers; the appropriate refactoring remains to be determined.

Written by the indexing model from the issue text.