Azure-sdk-for-java: [BUG] Memory leak in ServiceBusReceiverAsyncClient close

Describe the bug
When an instance of ServiceBusReceiverAsyncClient is created two LockContainer instance fields are created.

Each variable (in LockContainer's constructor) subscribe to Flux in order to cleanup resources periodically. The lambda used in the cleanup uses the lock container instance itself, so Flux will keep referencing the lock container instance until the consumer is disposed.

The issue is that when ServiceBusReceiverAsyncClient is closed, the LockContainer variables are not being also closed, which causes a memory leak.

To Reproduce
In order to reproduce create a ServiceBusReceiverAsyncClient instance and repeatedly call close and start. Use Visual VM in order to track memory use with heap dumps.

This is the memory use pattern you should see (a slight but steady increase in memory use):

And this is how the number of instances in the heap and their retained sizes will look like in time:

Expected behavior
LockContainer instances should be closed when the client is closed and therefore not leak into memory.

Setup (please complete the following information):

• OS: Mac/Linux
• IDE : IntelliJ
• 7.0.0

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