[multibody] Rename MbP output calc functions for uniformity

[jwnimmer-tri]

The output port named foo_bar is calculated via a member function named CalcFooBarOutput, with the output argument named 'output'.

Always use member functions for output ports, not gratuitously long lambdas with actual logic hiding inside of them.

Move the documentation about a ports' semantics from the private calc functions where nobody can find it, to the Doxygen public exposition of the ports. (In most cases it was already there, so we just remove the copy-pasted information.)

Deprecate some mis-matched port names and port getter names.

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Towards #21597 and therefore also #20545.

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This change is 

[jwnimmer-tri]

I think maybe sending to on-call platform reviewer is not the best way to handle this one.

Maybe one of @joemasterjohn or @xuchenhan-tri or @amcastro-tri would like to sign up as the second reviewer here, and then we can call that good (with Rico sufficient for platform review).