SearchBackPressure Policy/Decider Generic Framework Added

[CoderJeffrey]

Is your feature request related to a problem? Please provide an existing Issue # , or describe.

Previous work related to this PR:
For Search Back Pressure Service, previous PR (opensearch-project/performance-analyzer#483) (#427) (#437) have established a pipeline using Collector to read SearchBackPressure Cancellation Stats, using Reader to consume the metrics and populate to the sqlitedb, using Cluster/Node level RCA to consume stats in sqlitedb and compare stats with thresholds to generate Healthy/Unhealthy Flow Unit.

Problem:
We nee a Policy/Decider framework to suggest actions based on cluster level RCAs to tune the thresholds for SearchBackPressure Service.

Describe the solution you are proposing
This PR added the Policy/Decider Framework that consumed the cluster level RCA and suggestion actions to downstream classes.

Task Breakdown:

• Policy Class to determine when we need to suggest actions to user to auto-tune the thresholds for Search Back Pressure Service.
• Decider Class to consume the cluster-level RCA and use the Policy to send the actions to downstream classes.
• PolicyConfig file to read key thresholds/settings from Config files to improve extensibility for SearchBackPressureDecider.
• (Generic) Action Class for actions that will be sent to downstream classes to suggest user to tune the thresholds.

Describe alternatives you've considered
N/A

Additional context
Currently, the framework only suggest actions to tune heap related thresholds for Search Back Pressure Service.
Final policy logic to determine when to send out actions to users have not been decided yet. This PR mainly offers an extensible Decider/Policy framework.

Check List

• New functionality includes testing.
• All tests pass
• New functionality has been documented.
• New functionality has javadoc added
• Commits are signed per the DCO using --signoff

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