refactor: consolidate options inheritance logic

[HanaPearlman]

This PR introduces a new helper resolveOptions which includes the logic for inheriting some options from a parent. NOTE: It only merges in inherited properties (read/write concern, read preference, and bson options) from the parent, and does not add to or modify any other properties of options.

Options are resolved before a command is constructed. This means the options passed to CommandOperation are already properly inherited, and inheritance is no longer needed in the CommandOperation constructor. So, we can get rid of the NO_INHERIT_OPTIONS aspect and simply not call resolveOptions before those commands. Similarly, the ReadPreference.resolve() function is no longer needed.

There is also a change to ReadPreference.fromOptions(), where if the options don't have a readPreference property and a session is present on the options, we attempt to get the read preference from the session. This might have been intended all along, since the type of the options passed to this function, ReadPreferenceFromOptions, already had an optional session property.

NODE-2870

[HanaPearlman]

Note: ReadPreference.fromOptions should not default to primary if it cannot find a read pref in the options. In resolveOptions when ReadPreference.fromOptions is undefined, we default to the parent read pref. If fromOptions always defaults to primary, we would never use the parent read pref.

[mbroadst]

LGTM!

[nbbeeken]

LGTM-ing, my only comment is that we can do some documenting, the behavior isn't new so it's not critical but could be a good improvement. 👍

[nbbeeken]

I think we should add this to the function's docs for the ops that do this. Particularly with BSON options the return value could be unexpectedly different.