rewrite the docs on SQLite transaction handling

rewrite the docs on SQLite transaction handling

SQLite has added the new "connection.autocommit" mode and
associated fixes for pep-249 as of python 3.12.   they plan to
default to using this attribute as of python 3.16.   Get
on top of things by rewriting the whole doc section here, removing
old cruft about sqlalchemy isolation levels that was not correct
in any case, update recipes in a more succinct and unified way.

References: #12585
Change-Id: I9d1de8dcc27f1731ecd3c723718942148dcd0a1a