Optimize how we merge multiple operatorStats

[shangm2]

Description

1. Thanks to @arhimondr who observed that GC could take too much cpu to clean up memory during heavy load

2. This pr will be the first of a series of optimization to improve how objects are being created along the critical path.
3. This pr optimizes how we merge multiple operatorStats without creating temporary/intermediate objects

Motivation and Context

1. The original code will create temporary objects every time we add two OperatorStats together (with same id) using v.add(operatorStats) and this intermediate object will be discarded when it is used to merge with next OperatorStats object, This PR groups all operatorStats by their id and then merge them together in one go.
2. Refactoring the code by moving local variables into a dedicated class so that we can easily use one loop within the create method to aggregate all necessary metrics.

Impact

Test Plan

1. local hiveQueryRunner works fine
2. Internal verifier tests passed

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Release Notes

Please follow release notes guidelines and fill in the release notes below.

== RELEASE NOTES ==

Optimizations
* Improve how we merge multiple operator stats together. :pr:`24414`
* Improve metrics creation by refactoring local variables to a dedicated class. :pr:`24414`

[steveburnett]

Thanks for the release note! Rephrasing suggestions to follow the Order of changes in the Release Notes Guidelines:

== RELEASE NOTES ==

General Changes
* Improve how we merge multiple operator stats together. :pr:`24414`
* Improve metrics creation by refactoring local variables to a dedicated class. :pr:`24414`

[shangm2]

@arhimondr feel free to take another look. Thank you so much for all the awesome suggestionsl