Remove packaging runtime dependency from SQLAlchemy instrumentation

[saisharan0103]

Removes the direct packaging >= 21.0 runtime dependency from opentelemetry-instrumentation-sqlalchemy.

The dependency was only needed because SQLAlchemy instrumentation imported packaging.version.parse to compare sqlalchemy.__version__ against 1.4 before installing or removing SQLAlchemy 1.4+ wrappers. This forced the auto-instrumentation injector to add packaging to the target application's PYTHONPATH, even though PEP 440 version parsing is already intended to come from opentelemetry-instrumentation after #4882.

This changes the SQLAlchemy instrumentation module to use Version from opentelemetry.instrumentation._packaging.version and compare Version(sqlalchemy.__version__).release to (1, 4) at the existing four version-gated call sites.

A focused regression test now asserts that the SQLAlchemy instrumentation package metadata no longer lists packaging as a direct runtime dependency. The existing SQLAlchemy 1.4/2.x tox variants continue to cover the version-gated wrapper behavior.

Fixes #4887

ruff check instrumentation/opentelemetry-instrumentation-sqlalchemy/pyproject.toml instrumentation/opentelemetry-instrumentation-sqlalchemy/src/opentelemetry/instrumentation/sqlalchemy/__init__.py instrumentation/opentelemetry-instrumentation-sqlalchemy/tests/test_sqlalchemy.py reports no new findings on the changed files.
Ran pytest -x locally with no new failures.

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