Add cluster default remote store translog buffer interval setting

[ashking94]

Is your feature request related to a problem? Please describe.
This proposes to introduce a dynamic NodeScope settings i.e. cluster default remote store translog buffer interval setting. The index.remote_store.translog.buffer_interval setting currently has a default value of 650 ms which is picked up when the user does not provide an explicit index setting for the same. The 650ms value is known to outperform document replication index in terms of indexing throughput and latency with lesser CPU and memory consumption under settings with so workload (3 shard 1 replica, 3 cluster manager + 3 data nodes, aws instance type - r5.xlarge). However, the same buffer interval might not be the most suitable value for other workloads and configuration. Hence, there arises a need to keep the default configurable to allow the user to tune this and set a default that is most suitable to their needs.

Expected behaviour with the new setting -

• An index created without specifying the index.remote_store.translog.buffer_interval will use the cluster default.
• We are going to keep the same cluster default as being used by the above index setting - 650ms.
• If the cluster default is updated, then all the indexes that are using the cluster default will shift to the new updated value.
• If an index is created with overridden index setting, then it will continue to use the same even if the cluster default setting is udpated.

Describe the solution you'd like
Introduce the setting as mentioned above.

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
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