[10.x] Add Factory::getNamespace()

[tylernathanreed]

When overriding the Factory name guesser via Factory::guessFactoryNamesUsing(), I often need to know the current factory namespace. While I could certainly just hard-code Database\\Factories\\, that goes out the window if Factory::useNamespace() is used.

This PR just adds Factory::getNamespace() to return the static::$namespace property.

[flap152]

Note: In the end, static::$namespace was simply made public.
Shouldn't the PR be renamed to "[10.x] Make Factory::$namespace public"?

[tylernathanreed]

@flap152 I don't know if it's Taylor's practice to change PR titles. My original intent vs what got accepted are different.

[flap152]

I saw this PR through a Laravel Shift newsletter the referenced changes between releases with the title "Add getNamespace to Factory in #47463". It's also in the 10.14 Release content, issued yesterday, so renaming is probably a moot point, maybe impossible, possibly causing harm because it's been released.

I'm getting closer to contributing, looking at the process and "customs", and looking at the end result, I first wondered if there was a "magical getter" get{StaticProperty}() that turned a getNamespace() call into return static::$namespace 😅

I wonder if @taylorotwell did not notice the now-misleading title, or noticed but ignored it because he's busy, it's a small detail, etc. but not commenting on the change seemed odd to me. So the 1st line of my comment is to quickly notify other readers of the change in intent and implementation, the 2nd line is to maybe learn something.