[BUG] Getting timeout on graceful Shutdown in kinesis source.

Describe the bug
When graceful shutdown is called.
Kinesis source shutdown is getting timeout and proceeding with force shutdown.

To Reproduce
Steps to reproduce the behavior:

1. Start the data prepper
2. initiate graceful shutdown
3. Check the kinesis source shutdown log

Expected behavior

1. Timeout exception should not come.
2. Can the GRACEFUL_SHUTDOWN_WAIT_INTERVAL_SECONDS be configurable?

2025-07-18T15:55:58,854 [Thread-1] ERROR org.opensearch.dataprepper.plugins.kinesis.source.KinesisService 
- Exception while executing kinesis consumer graceful shutdown, doing force shutdown 
java.util.concurrent.TimeoutException: null at java.base/java.util.concurrent.CompletableFuture.timedGet(CompletableFuture.java:1892)
 ~[?:?] at java.base/java.util.concurrent.CompletableFuture.get(CompletableFuture.java:2027) ~[?:?] at 
org.opensearch.dataprepper.plugins.kinesis.source.KinesisService.shutDown(KinesisService.java:144) 
~[kinesis-source-2.12.0-SNAPSHOT.jar:?] at org.opensearch.dataprepper.plugins.kinesis.source.KinesisSource.stop(KinesisSource.java:69)
~[kinesis-source-2.12.0-SNAPSHOT.jar:?] at org.opensearch.dataprepper.core.pipeline.Pipeline.shutdown(Pipeline.java:304) 
~[data-prepper-core-2.12.0-SNAPSHOT.jar:?] at org.opensearch.dataprepper.core.DataPrepper.shutdownPipelines(DataPrepper.java:121) 
~[data-prepper-core-2.12.0-SNAPSHOT.jar:?] at org.opensearch.dataprepper.core.DataPrepper.shutdownPipelines(DataPrepper.java:106) 
~[data-prepper-core-2.12.0-SNAPSHOT.jar:?] at org.opensearch.dataprepper.core.DataPrepper.shutdown(DataPrepper.java:101) 
~[data-prepper-core-2.12.0-SNAPSHOT.jar:?] at org.opensearch.dataprepper.DataPrepperExecute.lambda<span>main</span>0(DataPrepperExecute.java:45) 
~[data-prepper-main-2.12.0-SNAPSHOT.jar:2.12.0-SNAPSHOT] at java.base/java.lang.Thread.run(Thread.java:829) [?:?]

Screenshots
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Environment (please complete the following information):

• OS: [e.g. Ubuntu 20.04 LTS]
• Version [e.g. 22]

Additional context
Add any other context about the problem here.

Start with the shutdown path shown in plugins/kinesis-source, especially KinesisService.shutDown at line 144 and KinesisSource.stop at line 69. Reproduce the graceful shutdown timeout, then trace how GRACEFUL_SHUTDOWN_WAIT_INTERVAL_SECONDS is used. Done means graceful shutdown no longer emits the timeout exception and the wait interval is configurable as requested.