Add external access integrations to SnowparkContainerJobOperator

[justinpakzad]

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This PR adds a new optional external_access_integrations parameter to the SnowparkContainerJobOperator. By default, application containers don’t have permission to access the internet, so this will enable users to provide the names of external access integrations so their jobs can access external sites. The new clause syntax comes straight from the Snowflake documentation. Fully backwards compatible as it's optional and defaults to None. The field was also added as a template field since it's a good candidate. Tests were added/updated to cover the new behavior.

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