refs #23395.

Complete rework of translating data values from database

Deprecation of SubfieldBase, removal of resolve_columns and
convert_values in favour of a more general converter based approach and
public API Field.from_db_value(). Now works seamlessly with aggregation,
.values() and raw queries.

Thanks to akaariai in particular for extensive advice and inspiration,
also to shaib, manfre and timograham for their reviews.

Allows easier customization of policies regarding which users are allowed to
reset their password.

Thanks Aymeric for review.

Thanks dgrant for the report.

Document that we should also offer sha256 checksums for packages

Changed comments in en_GB and en_AU formats files replacing 'pm' with
'p.m.' to match what is actually output.

This reverts commit a8521a2c.

Thanks to Trac alias nessita for the report.

Thanks kwist for the report and the initial patch.

Thanks to Trac user synasius and to Ola Sitarska for helping in
identifying the issue and helping with the test case.

Fixed #23364. Thanks Markush2010 for the report.

This change is needed for upcoming changes where settings might be
grouped in a parent dictionary.
Thanks Tim Graham for the review.

Thanks to Petr Glotov for spotting this.

refs #23323.