docs(env-args): added docs about instrumentation args and xctestrun-env

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (5d68e88) 59.24% compared to head (6d6253e) 59.24%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #902 +/- ## ========================================== Coverage 59.24% 59.24% Complexity 802 802 ========================================== Files 214 214 Lines 4468 4468 Branches 717 717 ========================================== Hits 2647 2647 Misses 1481 1481 Partials 340 340 ```

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