refactor(NODE-7089): make AggregateOperation subclass ModernizedOperation

[baileympearson]

Description

What is changing?

I broke this PR out of #4609 because it got kinda large.

This PR refactors AggregateOperation to subclass ModernizedOperation. Along the way, I encountered issues with omitReadPreference - an option which is used by the server class to remove a read preference from a command. To make this work with the existing design, the buildOptions method would need to start taking a reference to the connection to determine the maxWireVersion when attaching this option.

I didn't like this approach and this option is only used for the AggregateOperation when there is a write stage and we are using wire version <9, so I refactored to remove this option.

After removing omitReadPreference, it became clear we no longer needed trySecondaryWrite, which is also only used for Aggregation operations but is present on all operation classes, only used to determine if we should set omitReadPreference to true, and is assigned the same value has AggregateOperation.hasWriteStage.

After that I had a circular dependency because execute_operation now imports a reference to AggregateOperation. I broke the circular dependency by removing ExplainableCursor from explain.ts.

Is there new documentation needed for these changes?

What is the motivation for this change?

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