chore: prefix system tests env var (#10887)

Added prefix to env var to not conflict with local dev env vars

## Checklist
- [x] PR author has checked that all the criteria below are met
- The PR description includes an overview of the change
- The PR description articulates the motivation for the change
- The change includes tests OR the PR description describes a testing
strategy
- The PR description notes risks associated with the change, if any
- Newly-added code is easy to change
- The change follows the [library release note
guidelines](https://ddtrace.readthedocs.io/en/stable/releasenotes.html)
- The change includes or references documentation updates if necessary
- Backport labels are set (if
[applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting))

## Reviewer Checklist
- [x] Reviewer has checked that all the criteria below are met 
- Title is accurate
- All changes are related to the pull request's stated goal
- Avoids breaking
[API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces)
changes
- Testing strategy adequately addresses listed risks
- Newly-added code is easy to change
- Release note makes sense to a user of the library
- If necessary, author has acknowledged and discussed the performance
implications of this PR as reported in the benchmarks PR comment
- Backport labels are set in a manner that is consistent with the
[release branch maintenance
policy](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting)

.github/workflows/system-tests.yml

@@ -57,10 +57,8 @@ jobs:
       # If ever it's needed, a valid key exists in the repo, using ${{ secrets.DD_API_KEY }}
       DD_API_KEY: 1234567890abcdef1234567890abcdef
       CMAKE_BUILD_PARALLEL_LEVEL: 12
-      AWS_ACCESS_KEY_ID: ${{ secrets.IDM_AWS_ACCESS_KEY_ID }}
-      AWS_SECRET_ACCESS_KEY: ${{ secrets.IDM_AWS_SECRET_ACCESS_KEY }}
-      AWS_REGION:  us-east-1
-      AWS_DEFAULT_REGION: us-east-1  # AWS services should use `AWS_REGION`, but some still use the older `AWS_DEFAULT_REGION`
+      SYSTEM_TESTS_AWS_ACCESS_KEY_ID: ${{ secrets.IDM_AWS_ACCESS_KEY_ID }}
+      SYSTEM_TESTS_AWS_SECRET_ACCESS_KEY: ${{ secrets.IDM_AWS_SECRET_ACCESS_KEY }}
     steps:
 
       - name: Checkout system tests
@@ -109,10 +107,8 @@ jobs:
       # If ever it's needed, a valid key exists in the repo, using ${{ secrets.DD_API_KEY }}
       DD_API_KEY: 1234567890abcdef1234567890abcdef
       CMAKE_BUILD_PARALLEL_LEVEL: 12
-      AWS_ACCESS_KEY_ID: ${{ secrets.IDM_AWS_ACCESS_KEY_ID }}
-      AWS_SECRET_ACCESS_KEY: ${{ secrets.IDM_AWS_SECRET_ACCESS_KEY }}
-      AWS_REGION:  us-east-1
-      AWS_DEFAULT_REGION: us-east-1  # AWS services should use `AWS_REGION`, but some still use the older `AWS_DEFAULT_REGION`
+      SYSTEM_TESTS_AWS_ACCESS_KEY_ID: ${{ secrets.IDM_AWS_ACCESS_KEY_ID }}
+      SYSTEM_TESTS_AWS_SECRET_ACCESS_KEY: ${{ secrets.IDM_AWS_SECRET_ACCESS_KEY }}
     steps:
 
       - name: Checkout system tests