Add Update without returning (#2965)

* Update without returning

* Fix update_without_returning compile error; add tests

ActiveModelTrait::update_without_returning called the non-existent
Self::Entity::update_without_returning(am); use Self::Entity::update(am),
whose UpdateOne gains the new exec_without_returning.

Add integration tests covering a successful update, RecordNotUpdated on a
non-existent row, before_save running, and after_save being skipped.

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Co-authored-by: Chris Tsang <chris.2y3@outlook.com>