chore(iast): improve ast patching allowlist [backport 2.21]

[avara1986]

Backport #13021 to 2.21

This PR improves the AST patching allowlist mechanism to better handle third-party modules. The changes include:

• Enhanced allowlist logic in iastpatch.c for third-party module detection
• Improved string comparison in AST patching to properly handle module paths

These changes make the IAST module patching more reliable and maintainable, while ensuring proper handling of third-party modules like psycopg2.

Related to: APPSEC-56946 &
#13017

(cherry picked from commit 0b25c11)

Checklist

• 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
• The change includes or references documentation updates if necessary
• Backport labels are set (if applicable)

Reviewer Checklist

• 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 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

[github-actions]

CODEOWNERS have been resolved as:

ddtrace/appsec/_iast/_ast/iastpatch.c                                   @DataDog/asm-python
tests/appsec/iast/_ast/test_ast_patching.py                             @DataDog/asm-python
tests/appsec/iast/conftest.py                                           @DataDog/asm-python
tests/appsec/iast/iast_utils.py                                         @DataDog/asm-python
tests/appsec/iast/test_env_var.py                                       @DataDog/asm-python
tests/appsec/iast/test_iast_propagation_path.py                         @DataDog/asm-python
tests/appsec/iast_packages/test_packages.py                             @DataDog/asm-python

[pr-commenter]

Benchmarks

Benchmark execution time: 2025-04-03 12:03:00

Comparing candidate commit dd6907b in PR branch backport-13021-to-2.21 with baseline commit 8015b10 in branch 2.21.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 418 metrics, 2 unstable metrics.