Add factory_bot.before_factory_run instrumentation event

[donny741]

Problem this feature will solve

I need to implement a factory call stack that can be displayed in the error message that is raised from factory's after callback.

Factories can be deeply nested into one another and when the error message is displayed, it is hard to track down the path that led to the error because only the top-level factory is displayed in the message, and stack trace does not include nested factories.

Desired solution

Add ActiveSupport::Notifications.instrument("factory_bot.before_factory_run", instrumentation_payload) to factory_runner.rb before L28

Alternatives considered

Using Global callbacks, however, I cannot find a way to get the factory name from within the callback.

Using factory_bot.compile_factory event instead. Works only when running a single spec, with multiple specs, the compiled factories are cached and the event is no longer invoked.