Lazy load snowflake imports to improve performance

[dwreeves]

This PR lazy-loads Snowflake modules to improve performance when importing from airflow.providers.snowflake.

Because SnowflakeSqlApiHook is a subclass of SnowflakeHook, and the operators module imports the SnowflakeSqlApiHook globally, this improves the load time of effectively every import from airflow.providers.snowflake and puts significantly less stress on the scheduler instance when parsing the DAG.

See linked issue for full benchmarking code. TLDR, the cost of importing Snowflake modules is fairly significant:

─────────────────────────── Snowflake Hook — Import Cost Benchmark ───────────────────────────
  Python: 3.13.1 (main, Jan 14 2025, 23:48:54) [Clang 19.1.6 ]
  Runs per scenario: 10  |  also benchmark w/o .pyc: no

            avg ms (±stdev)  |  avg RSS MB  —  10 runs each             
╭───────────────────────────────┬───────────────────┬──────────────────╮
│ Scenario                      │ Time w/ .pyc (ms) │ RSS w/ .pyc (MB) │
├───────────────────────────────┼───────────────────┼──────────────────┤
│ No Snowflake, no SQLAlchemy   │             60 ±2 │             17.2 │
│ No Snowflake, yes SQLAlchemy  │     121 ±1  (+61) │    31.0  (+13.9) │
│ Yes Snowflake, yes SQLAlchemy │    291 ±5  (+231) │    59.8  (+42.6) │
╰───────────────────────────────┴───────────────────┴──────────────────╯
  (+N) = delta vs first scenario  |  ±N = stdev across runs

The one thing I am unclear about is covering this with tests. I have written code before which asserts the non-import of a module, and I also see this in some cases in Airflow (see [1], [2]), however I'm not sure if that's done generally or if it makes sense here.

• closes: [Feat] [Snowflake Provider] Lazy import of snowflake modules in snowflake/hooks/snowflake.py #62362

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Was generative AI tooling used to co-author this PR?

• Yes (please specify the tool below)

(No AI code is present in this commit. However, I did use code generated by Claude to help benchmark the performance improvement.)