Passes through IntegrityErrors that are not ReadOnlyEntryErrors

Co-authored-by: Alex Fikl <alexfikl@gmail.com>

Co-authored-by: Andreas Kloeckner <inform@tiker.net>

* KeyBuilder: add datetime hashing

* (try to) take naive/aware, timezones into account

* add another test

* fix datetime timezones

* another time fix

* clean up some version_info checks

* change name to pytools.tag

* better docs, type annotations

* more annotations

* add to README

* make it generic

* fix doc

* complete annotations

* improve KeyBuilder documentation

* clarify slightly

* Tweak docs, add types

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Co-authored-by: Andreas Kloeckner <inform@tiker.net>

This reverts commit 0b4604cc.

* Record: make field ordering deterministic

* add set conversion to __setstate__

* remove duplicate/unnecessary definitions

* add warning

* fix register_fields

* improve tests

* add pickle test

* restore __slots__ in Record, add to test

* better warning

* add type annotations