PHPLIB-802: Send readConcern but not writeConcern to explain commands

[GromNaN]

Fix PHPLIB-802

ReadConcern is relevant for query plan evaluation, not WriteConcern (comment)

This should be covered by unit tests PHPLIB-1144.

[jmikola]

I noted the discussion in SERVER-28678 that readConcern might be relevant but writeConcern is not. Feel free to amend the original title/description of PHPLIB-802 to accurately reflect the change.

[jmikola]

readConcern should not be added directly to the command document. The option is already handled in executeCommand() along with other options for the execute method.

That code path allows for sensible inheritance of client-level options. I'd have to double-check libmongoc internals to confirm, but I think directly adding it in a command document here might result in duplicate BSON fields being sent to the server. I know that's possible if you were to manually inject a session ID in the lsid field.

Instead, I think you should add this option in getCommandDocument(). You can use the array union operator to do so and just add ['readConcern' => ...] to $this->createCommandDocument() before returning. A more verbose approach with an assigned variable is fine as well.

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Likewise for other Explainable commands where you modified the value used to construct the Command object instead of the Explainable::getCommandDocument() implementation.

[GromNaN]

I understand better how it works now.
I opted for the more verbose way to add the readConcern option when available: its easier to read and better for code analysis.

[jmikola]

The Find operation has never documented a writeConcern option. Moreover, createQueryOptions() never creates a writeConcern key in its return array. This can be removed.

[jmikola]

LGTM after removing the change to FindAndModify.php.

You may also want to rebase and regenerate the psalm baseline before merging, rather than attempt to resolve that conflict through GitHub's UI.