Remove redundant Snowflake prefixes from Cortex Agent and SQL API modules

[SameerMesiah97]

Description

This change renames the Snowflake Cortex Agent hook and operator modules to cortex_agent.py, and the SQL API hook module to sql_api.py.

Imports, mock targets, corresponding test filenames, documentation and provider metadata are updated to use the new module paths.

Rationale

In line with AIP-21, this change removes redundant provider prefixes from module names. The snowflake_ prefix repeats information already provided by the airflow.providers.snowflake package.

Removing it makes these module paths shorter while retaining descriptive filenames and keeping class names unchanged.

Tests

• Updated existing hook and operator tests to use the new module paths.
• Added compatibility tests verifying that old imports emit deprecation warnings and resolve to the same classes as the new imports.

Backwards Compatibility

Existing import paths remain available through add_deprecated_classes() mappings in the hook and operator packages. Existing DAGs continue to work, with deprecation warnings directing users to the new paths.

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