[Spark] Structured streaming runner: asynchronous cancel() should not report CANCELLED before the execution ended

[tkaymak]

SparkStructuredStreamingPipelineResult.cancel() requests cancellation asynchronously and sets the state to CANCELLED at once. Per the PipelineResult contract the state should be observed: getState() queries the execution, waitUntilFinish() blocks until the pipeline is actually cancelled on the (mini) cluster, and only then the state becomes CANCELLED.

Changing this touches the shared StructuredStreamingPipelineStateTest, which asserts CANCELLED right after cancel() for the batch path today, and the legacy SparkPipelineResult has the same shape. Scope: runners/spark/src/main/java/org/apache/beam/runners/spark/structuredstreaming/SparkStructuredStreamingPipelineResult.java and that test.

Follow up from #40103 / Part of #36841

[tkaymak]

Also part of this: cancel() called after the execution already ended, but before anyone observed it, currently reports CANCELLED instead of the real DONE or FAILED. The state query should resolve that from the execution.