[5.7] Add model factory type annotation

[jmsfwk]

Adding the type annotation to the model factory stub will help autocompletion tools to provide method suggestions.

This is more useful for methods like state() or afterCreating() that might not be used as often as define().

[ahinkle]

See #24647

[driesvints]

Please see linked PR above

[deleugpn]

This was added and removed and added and removed countless of times. Last time it was added, Graham simply removed it because it was /* instead of /** and he thinks it's an invalid docblocks and phpstorm is wrong for understanding it.