Fix Python 3.10 compatibility: Replace datetime.UTC with timezone.utc

- Created datetime_compat module to provide UTC constant using timezone.utc
- Updated all direct UTC imports to use compatibility module
- Added tests to verify UTC timezone compatibility
- Fixes #2171

Co-Authored-By: Joe Moura <joao@crewai.com>

src/crewai/utilities/datetime_compat.py

@@ -0,0 +1,6 @@
+"""Compatibility module for datetime functionality across Python versions."""
+from datetime import timezone
+
+# Provide UTC timezone constant that works in Python 3.10+
+# This is equivalent to datetime.UTC in Python 3.11+
+UTC = timezone.utc