Fix ignored direct time travel parameters in DataFrameReader

[fallintoplace]

Summary

• recognize direct statement, offset, timestamp, and stream arguments when choosing the time-travel parameter path
• preserve the documented behavior that direct parameters override reader options
• add public API regression coverage for each affected selector

Previously, DataFrameReader.table() only selected the direct-parameter path when time_travel_mode or an Iceberg-specific argument was set. A selector such as offset=-60 was therefore dropped before reaching Session.table, silently returning the current table instead of raising the existing missing-mode validation error.

Testing

• python -m pytest tests/unit/test_dataframe.py tests/unit/test_utils.py -q
• pre-commit run --files src/snowflake/snowpark/dataframe_reader.py tests/unit/test_dataframe.py

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[fallintoplace]

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