chore(tests): pin system tests to a specific commit (#6780)

- pin system tests to a specific commit
- add python-guild as owner to system test config file for github
actions

This PR proposes the same solution for handling simultaneous changes as
the java tracer. System tests will be pin to a specific commit and any
PR that requires system test changes could:

- first, commit specific changes into system tests main branch
- then, add the new hash commit to the PR for the Python tracer

## Checklist

- [x] Change(s) are motivated and described in the PR description.
- [x] Testing strategy is described if automated tests are not included
in the PR.
- [x] Risk is outlined (performance impact, potential for breakage,
maintainability, etc).
- [x] Change is maintainable (easy to change, telemetry, documentation).
- [x] [Library release note
guidelines](https://ddtrace.readthedocs.io/en/stable/releasenotes.html)
are followed. If no release note is required, add label
`changelog/no-changelog`.
- [x] Documentation is included (in-code, generated user docs, [public
corp docs](https://github.com/DataDog/documentation/)).
- [x] Backport labels are set (if
[applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting))

## Reviewer Checklist

- [x] Title is accurate.
- [x] No unnecessary changes are introduced.
- [x] Description motivates each change.
- [x] Avoids breaking
[API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces)
changes unless absolutely necessary.
- [x] Testing strategy adequately addresses listed risk(s).
- [x] Change is maintainable (easy to change, telemetry, documentation).
- [x] Release note makes sense to a user of the library.
- [x] Reviewer has explicitly acknowledged and discussed the performance
implications of this PR as reported in the benchmarks PR comment.
- [x] 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)
- [x] If this PR touches code that signs or publishes builds or
packages, or handles credentials of any kind, I've requested a review
from `@DataDog/security-design-and-guidance`.
- [x] This PR doesn't touch any of that.

---------

Co-authored-by: Tahir H. Butt <[email protected]>

Author: christophe-papazian

.github/CODEOWNERS

@@ -84,4 +84,5 @@ mypy.ini                            @DataDog/python-guild  @DataDog/apm-core-pyt
 .github/PULL_REQUEST_TEMPLATE.md    @DataDog/python-guild  @DataDog/apm-core-python
 .github/ISSUE_TEMPLATE.md           @DataDog/python-guild  @DataDog/apm-core-python
 .github/CODEOWNERS                  @DataDog/python-guild  @DataDog/apm-core-python
+.github/workflows/system-tests.yml  @DataDog/python-guild  @DataDog/apm-core-python
 ddtrace/internal/compat.py          @DataDog/python-guild  @DataDog/apm-core-python

.github/workflows/system-tests.yml

@@ -54,6 +54,7 @@ jobs:
         uses: actions/checkout@v3
         with:
           repository: 'DataDog/system-tests'
+          ref: '49e9abbe3f83a680a509eaf19c7649e26509e08a'
 
       - name: Checkout dd-trace-py
         if: needs.needs-run.outputs.outcome == 'success'
@@ -163,6 +164,7 @@ jobs:
         uses: actions/checkout@v3
         with:
           repository: 'DataDog/system-tests'
+          ref: '49e9abbe3f83a680a509eaf19c7649e26509e08a'
 
       - uses: actions/setup-python@v4
         if: needs.needs-run.outputs.outcome == 'success'