fix: upgrade to elasticsearch-py 7.17.13 and opensearch-py 2.x for urllib3 2.x compatibility

[dpgaspar]

Summary

• Upgrades elasticsearch-py to >=7.17.13, <8 which supports urllib3 2.x on Python 3.10+, resolving connection failures on modern Python environments
• Adds opensearch-py>=2.4.0, <3 as a direct dependency for OpenSearch support
• Updates CI to test against all three backends: ES 7.x, ES 8.x (via compatibility mode with ELASTIC_CLIENT_APIVERSIONING=1), and OpenSearch 2.x
• Updates SQLAlchemy integration to 2.x API (URL.create, text(), import_dbapi(), ReflectedColumn, etc.)
• Requires Python 3.10+ (drops 3.6–3.9)

Changes

Dependencies (setup.py, requirements-dev.txt)

• elasticsearch>=7.17.13, <8 (was >=7.x, <7.14)
• opensearch-py>=2.4.0, <3 (new direct dependency)
• Pinned dev dependencies matching modern toolchain

Core (es/baseapi.py, es/elastic/api.py, es/opendistro/api.py)

• Dual exception handling for both elasticsearch and opensearchpy exceptions
• Conditional Content-Type header: ES 7.x client needs explicit header, OpenSearch client sets it automatically
• Filter cursor-specific params (sql_path, fetch_size, time_zone, v2) from client kwargs
• Class-level type annotations for self.es in Connection subclasses

SQLAlchemy (es/basesqlalchemy.py, es/elastic/sqlalchemy.py, es/opendistro/sqlalchemy.py)

• Added import_dbapi() classmethod on all dialect classes (SA 2.x requirement)
• supports_statement_cache = False
• get_type() returns TypeEngine instances (not classes)
• get_columns() returns List[ReflectedColumn]

Tests & CI

• SQLAlchemy 2.x test API: URL.create(), text(), inspect(), autoload_with=
• CI matrix tests against ES 7.17.27, ES 8.17.0, and OpenSearch 2.19.0
• Docker Compose updated with all three services

Test plan

• 48/48 tests pass on ES 7.17.27
• 48/48 tests pass on ES 8.17.0 (compatibility mode)
• 48/48 tests pass on OpenSearch 2.19.0
• Linting passes: black, flake8, mypy (8 pre-existing errors, 0 new)
• CI pipeline passes on GitHub Actions

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