fix: avoid early and potentially unneeded iast import [backport 1.18] (#6722)

Backport edc7a42 from #6721 to 1.18.

## 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: Juanjo Alvarez Martinez <[email protected]>

Author: github-actions[bot]

ddtrace/contrib/subprocess/patch.py

@@ -17,7 +17,6 @@
 
 from ddtrace import Pin
 from ddtrace import config
-from ddtrace.appsec.iast.taint_sinks.command_injection import CommandInjection
 from ddtrace.contrib import trace_utils
 from ddtrace.contrib.subprocess.constants import COMMANDS
 from ddtrace.ext import SpanTypes
@@ -197,6 +196,8 @@ def __init__(self, shell_args, shell=False):
         )
 
         if report_cmdi:
+            from ddtrace.appsec.iast.taint_sinks.command_injection import CommandInjection
+
             CommandInjection.report(evidence_value=report_cmdi)
 
     def scrub_env_vars(self, tokens):

releasenotes/notes/asm-avoid-subprocess-iast-import-2e4b354d5880de40.yaml

@@ -0,0 +1,3 @@
+fixes:
+  - |
+    ASM: avoid potentially unneeded import of the IAST native module.