fix improper names of several special functions for CBF #32869
Description
CBF, i.e. sage/rings/complex_arb.pyx, names functions such as Ei impoperly, as ei. This in particular makes it impossible to do e.g. CBF(Ei(I)) (one gets infinite recursion error).
The fix is just to rename them. One can first set aliases Ei = ei, etc.,
and deprecate ei, and then, after the deprecation period, do the renaming.
Component: symbolics
Author: Marc Mezzarobba
Branch/Commit: d9ee935
Reviewer: Dima Pasechnik
Issue created by migration from https://trac.sagemath.org/ticket/32869