Fix(Amazon): Restore wait_policy in EmrCreateJobFlowOperator

[dv-gorasiya]

Description
Restores the functionality of the wait_policy parameter in EmrCreateJobFlowOperator.
Previously, wait_policy was deprecated and ignored in favor of a hardcoded 'running' state check when wait_for_completion was True.
This change allows users to explicitly specify policies like WAIT_FOR_STEPS_COMPLETION (to wait for cluster termination) while maintaining backward compatibility (implied wait_for_completion=True).

Related Issue
Closes #61180

Tests
Added test_execute_with_wait_policy to verify the correct waiter is used.
Removed test_wait_policy_deprecation_warning as the parameter is no longer deprecated.

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[phanikumv]

Seems to be a duplicate of https://github.com/apache/airflow/pull/61195/changes?

[dv-gorasiya]

Closing in favor of #61195, which covers the same fix and includes better test coverage and deferrable support. Thanks @phanikumv for pointing it out!