This is the immutability ticket for sections (cf. #30261).

In this ticket we also add most features that have been developed in the last Sage versions and not been adapted to sections yet. This includes:

• _is_zero attribute
• unsafe assignments
• copy_from method

Follow up: #31255

CC: @egourgoulhon @tscrim @mkoeppe

Component: manifolds

Keywords: immutable

Author: Michael Jung

Branch: 04085f9

Reviewer: Matthias Koeppe

Issue created by migration from https://trac.sagemath.org/ticket/30288