Remove System and Environment config source in the CoreTracer

[mariusc83]

What does this PR do?

We are removing the System and Environment config sources in the CoreTracer as we are not using those in the Android JVM.

Motivation

What inspired you to submit this pull request?

Additional Notes

Given this is a quite important update I am not sure if we should merge it or not. Let me know your thoughts.

Review checklist (to be filled by reviewers)

• [ ] Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• [ ] Make sure you discussed the feature or bugfix with the maintaining team in an Issue
• [ ] Make sure each commit and the PR mention the Issue number (cf the CONTRIBUTING doc)

[codecov-commenter]

Codecov Report

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

Project coverage is 69.03%. Comparing base (5197289) to head (be02165). Report is 4 commits behind head on develop.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #2084 +/- ## =========================================== + Coverage 68.73% 69.03% +0.31% =========================================== Files 719 708 -11 Lines 26571 26300 -271 Branches 4472 4424 -48 =========================================== - Hits 18262 18156 -106 + Misses 7123 6939 -184 - Partials 1186 1205 +19 ``` | [Files](https://app.codecov.io/gh/DataDog/dd-sdk-android/pull/2084?dropdown=coverage&src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=DataDog) | Coverage Δ | | |---|---|---| | [...ce/src/main/java/com/datadog/trace/api/Config.java](https://app.codecov.io/gh/DataDog/dd-sdk-android/pull/2084?src=pr&el=tree&filepath=features%2Fdd-sdk-android-trace%2Fsrc%2Fmain%2Fjava%2Fcom%2Fdatadog%2Ftrace%2Fapi%2FConfig.java&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=DataDog#diff-ZmVhdHVyZXMvZGQtc2RrLWFuZHJvaWQtdHJhY2Uvc3JjL21haW4vamF2YS9jb20vZGF0YWRvZy90cmFjZS9hcGkvQ29uZmlnLmphdmE=) | `62.57% <100.00%> (-1.01%)` | :arrow_down: | | [...race/bootstrap/config/provider/ConfigProvider.java](https://app.codecov.io/gh/DataDog/dd-sdk-android/pull/2084?src=pr&el=tree&filepath=features%2Fdd-sdk-android-trace%2Fsrc%2Fmain%2Fjava%2Fcom%2Fdatadog%2Ftrace%2Fbootstrap%2Fconfig%2Fprovider%2FConfigProvider.java&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=DataDog#diff-ZmVhdHVyZXMvZGQtc2RrLWFuZHJvaWQtdHJhY2Uvc3JjL21haW4vamF2YS9jb20vZGF0YWRvZy90cmFjZS9ib290c3RyYXAvY29uZmlnL3Byb3ZpZGVyL0NvbmZpZ1Byb3ZpZGVyLmphdmE=) | `61.11% <100.00%> (-0.55%)` | :arrow_down: | | [...c/main/java/com/datadog/trace/core/CoreTracer.java](https://app.codecov.io/gh/DataDog/dd-sdk-android/pull/2084?src=pr&el=tree&filepath=features%2Fdd-sdk-android-trace%2Fsrc%2Fmain%2Fjava%2Fcom%2Fdatadog%2Ftrace%2Fcore%2FCoreTracer.java&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=DataDog#diff-ZmVhdHVyZXMvZGQtc2RrLWFuZHJvaWQtdHJhY2Uvc3JjL21haW4vamF2YS9jb20vZGF0YWRvZy90cmFjZS9jb3JlL0NvcmVUcmFjZXIuamF2YQ==) | `70.71% <ø> (-0.83%)` | :arrow_down: | ... and [31 files with indirect coverage changes](https://app.codecov.io/gh/DataDog/dd-sdk-android/pull/2084/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=DataDog)