At the moment, (many) multivariate laurent polynomials and their rings are expensively converted when passed through _element_constructor_. The aim of this ticket is to detect a couple of special cases, where this can be done more directly, e.g., if the to-be-converted element has the same parent or the same polynomial ring as the laurent polynomial ring.

Along the way, I pickling bug is fixed.

Depends on #21855
Depends on #21968

Component: algebra

Author: Daniel Krenn

Branch/Commit: 1b7377c

Reviewer: Clemens Heuberger, Travis Scrimshaw

Issue created by migration from https://trac.sagemath.org/ticket/21976