Add transaction-related events to the Database API

For inspiration see https://github.com/laravel/framework/tree/10.x/src/Illuminate/Database/E...

Reparenting.

On this

Started something, fit nicely with latest improvements in 📌 Refactor transactions Fixed . Looking forward to an early review - this sets the basis, more events are just more meat around this bone.

Postponed on 🐛 Strengthen TransactionManager Needs work

rebased

We cannot do this now, 🐛 Transaction autocommit during shutdown relies on unreliable object destruction order (xdebug 3.3+ enabled) Needs review introduced Database::commitAllOnShutdown() which runs at a time when the event dispatcher has been destroyed already, so events fail. One more reason to move towards explicit commit.

eesh, seems not-ideal to wait until most-everything is destroyed to commit transactions, i.e. difficult to respond to various transaction commit failure modes.