Include Environment Variables in JSON output in easier-to-parse form

If I run a set of benchmarks with

`dotnet run -c:Release -- -f *Log* --runtimes net8.0 --envVars x:1 y:2`

And export a JSON report, the JSON contains the environment variables embedded in the DisplayInfo:

```json
"DisplayInfo":"LogBenchmark.TrackTrace: Job-OTYZFP(EnvironmentVariables=x=1,y=2, Runtime=.NET 8.0, Toolchain=net8.0, IterationCount=3, LaunchCount=1, WarmupCount=3)"
```

But I would like to be able to extract the environment variable values more easily from the report for further processing. What if there was an additional property bag in the report?

Something like:

```json
"EnvironmentVars": {
"x": "1",
"y:" "2"
}
```