fix(debugging): use millisecond for duration in expression DSL [backport 1.18] (#6766)

Backport b97591c from #6732 to 1.18.

We convert the `@duration` injected local variable in milliseconds to
match the UI expectation and report correct numbers.

## 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)

Co-authored-by: Gabriele N. Tornetta <[email protected]>

Author: github-actions[bot]

ddtrace/debugging/_signal/model.py

@@ -84,7 +84,7 @@ def _eval_condition(self, _locals=None):
 
     def _enrich_args(self, retval, exc_info, duration):
         _locals = list(self.args or safety.get_args(self.frame))
-        _locals.append(("@duration", duration))
+        _locals.append(("@duration", duration / 1e6))  # milliseconds
         if exc_info[1] is None:
             _locals.append(("@return", retval))
         return dict(_locals)

releasenotes/notes/fix-debugger-duration-ms-in-dsl-aad91c0b730bbdf0.yaml

@@ -0,0 +1,5 @@
+---
+fixes:
+  - |
+    dynamic instrumentation: function duration measurements are now reported in
+    milliseconds to match the expectation from the UI.

tests/debugging/signal/test_model.py

@@ -0,0 +1,22 @@
+import sys
+from threading import current_thread
+
+from ddtrace.debugging._signal.snapshot import Snapshot
+from tests.debugging.utils import create_log_function_probe
+
+
+def test_duration_millis():
+    duration = 123456
+    args = Snapshot(
+        probe=create_log_function_probe(
+            probe_id="test_duration_millis",
+            module="foo",
+            func_qname="bar",
+            template="",
+            segments=[],
+        ),
+        frame=sys._getframe(),
+        thread=current_thread(),
+    )._enrich_args(None, (None, None, None), duration)
+
+    assert args["@duration"] == duration / 1e6