gh-83638: Add sqlite3.Connection.autocommit for PEP 249 compliant behaviour (#93823)

Introduce the autocommit attribute to Connection and the autocommit
parameter to connect() for PEP 249-compliant transaction handling.

Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>
Co-authored-by: C.A.M. Gerlach <CAM.Gerlach@Gerlach.CAM>
Co-authored-by: Géry Ogam <gery.ogam@gmail.com>