Fix logging of plan optimizer

[feilong-liu]

Description

Change the result type of PlanOptimizer, so that it not only returns the new plan node, but also returns whether the optimizer is triggered or not.

Motivation and Context

Currently, the logging of PlanOptimizer is to compare the old and new plan root with the equal operator. However, this leads to false positives, where any non meaningful changes (for example reorder of outputs etc) will show as optimizer triggered. It also relies on proper equal() override for all data structures in query plans.

In this PR, I change the PlanOptimizer to explicitly return whether an optimizer is triggered or not. I've implemented them for all existing plan optimizers.

Impact

Fix logging of optimizers, and eliminate false positives.

Test Plan

Existing unit tests.

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Release Notes

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== RELEASE NOTES ==

General Changes
* Fix logging of optimizer triggering, eliminating false positives where optimizer is logged as triggered but actually not. The PlanOptimizer now return both result plan and whether the plan changed or not.

[mlyublena]

Thanks for fixing these!

[mlyublena]

are we sure that this optimizer added the exchange node and it wasn't there before?

[feilong-liu]

Yes, we only have this optimizer to add remote exchange node.

[feilong-liu]

Instead of comparing plan node, now the optimizer returns whether the plan is changed or not.

[pranjalssh]

Will all new optimizers will have to implement isOptimizerTriggered method. So all spi optimizers and our internal optimizers api might change. Please add that in release notes