SNOW-2912540: mock _connect on v5 so local testing skips UD connection_init

[sfc-gh-fpawlowski]

Summary

MockedSnowflakeConnection (Local Testing's mock connection class) subclasses the real SnowflakeConnection and overrides connect() to a no-op, avoiding a real network connection attempt during local testing sessions.

On v5 (UD), Connection.__init__ calls the private _connect() internally instead of the public connect() the legacy v4 connector called. Since the mock override was only named connect, UD's real _connect() ran unmocked on IS_V5_DRIVER=True, attempting a genuine connection attempt requiring real account credentials — surfacing as an account/credentials error in local-testing sessions that should never touch the network at all.

Fix: on v5, alias _connect = connect so the existing mock override is actually invoked by UD's __init__ path.

Known gap: no dedicated test exercises this specific IS_V5_DRIVER=True code path (unverifiable without a UD wheel installed, same caveat as the rest of this stack). Flagging for reviewer awareness rather than holding up this draft.

Stacked on #4321.

Test plan

• flake8/black clean
• Full tests/unit/+tests/mock/ suite passes for v4 (2916 passed) — this branch doesn't change v4 behavior at all
• No test coverage for the IS_V5_DRIVER=True path itself

🤖 Generated with Claude Code

[sfc-gh-fpawlowski]

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• SNOW-2912540: mock _connect on v5 so local testing skips UD connection_init #4326 👈 (View in Graphite)
• SNOW-2912540: mock-patch try_add_log_to_batch instead of reading _log_batch #4321 : 1 other dependent PR (#4322 )
• SNOW-2912540: use IS_V5_DRIVER for cursor request_id access #4314 : 1 other dependent PR (#4317 )
• SNOW-2912540: add IS_V5_DRIVER constant; use it for SecretDetector/TelemetryData/TelemetryClient/ReauthenticationRequest imports and pandas/pyarrow/numpy resolution #4313
• SNOW-2912540: decouple LocalTestOOBTelemetryService from connector.telemetry_oob #4309 : 1 other dependent PR (#4310 )
• SNOW-2912540: inline _create_temp_stage and _create_temp_file_format into analyzer_utils #4308
• SNOW-2912540: define ASYNC_RETRY_PATTERN and compat.OK locally #4282
• SNOW-2912540: translate create_temp_table=True to table_type in AST encoding (rebased onto main) #4307
• main

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