[Filebeat] aws-s3 - Add s3_objects_tracked metric

[andrewkroh]

Add a new metric to the aws-s3 input to observe the number of S3 Objects being tracked in the input's state.

This metric will be useful as a proxy for memory used by the input (since it keeps the states loaded in memory) and as a very rough way of understanding how many objects the inputs has to list for each full scan.

The proposed name and definition are:

• s3_objects_tracked_gauge : Number of S3 object tracked by the input when in bucket listing mode.

[botelastic[bot]]

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