Improve doctest coverage of misc/fpickle.pyx

[saraedum]

I introduced some functions without doctests in #11716. This ticket tries to add the missing doctests to the these and other functions in that file.

This is part of doctest meta-ticket #12024.

Depends on #11819

Component: doctest coverage

Keywords: sd35

Work Issues: author needs to check the rebase

Author: Julian Rüth

Branch/Commit: u/saraedum/ticket/12192 @ c6ae8c9

Reviewer: Travis Scrimshaw

Issue created by migration from https://trac.sagemath.org/ticket/12192

[saraedum]

Author: Julian Rueth

[saraedum]

comment:1

With the patch, -coverage gives:
SCORE devel/sage/sage/misc/fpickle.pyx: 100% (9 of 9)

[saraedum]

Attachment: trac_12192.patch.gz

added docstrings

[saraedum]

comment:2

I also moved call_pickled_function to where it belongs imho.

[saraedum]

Changed keywords from none to sd35

[tscrim]

Reviewer: Travis Scrimshaw

[tscrim]

comment:5

A few things:

• Add fpickle documentation by modifying misc.rst.

• Remove the second colon : from pickle_code().

• Use automatic trac linking :trac:`11716`.

• Use ``None`` in code format in the documentation (only place I see this not used it in unpickleMethod() inputs)

Thanks.