[improve][broker] Added synchronized for sendMessages in Non-Persistent message dispatchers

[sandeep-mst]

Fixes apache#24379

Motivation

We have observed inconsistency with the usage of synchronized keyword while dispatching messages to the consumer across different dispatchers.
The following are not using synchronized keyword while filtering and sending messages to the consumers.

• NonPersistentDispatcherSingleActiveConsumer#sendMessages
• NonPersistentStickyKeyDispatcherMultipleConsumers#sendMessages

The rest of the dispatchers including all the persistent dispatchers and NonPersistentDispatcherMultipleConsumers use synchronized while sending messages. This causes inconsistencies across different dispatchers while running server-side filters with multiple producers and a single consumer as it will get multi-threaded. This is even more a case when server-side filter code is not thread-safe.

Modifications

Added synchronized keyword at the following two method calls.

• NonPersistentDispatcherSingleActiveConsumer#sendMessages
• NonPersistentStickyKeyDispatcherMultipleConsumers#sendMessages

Verifying this change

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Matching PR in forked repository

PR in forked repository:

[sandeep-mst]

Closing as PR is merged upstream and synced to fork master.
apache#24386