[5.4] Add ability to keep old files when testing uploads [second attempt]

[gocanto]

Hi guys,

This is my second attempt to get this behavior into the framework.

This PR had been closed in the past due to the uses of Boolean variables. It does not introduce breaking changes because it keeps the actual behavior by default.

They way how it can be used is like so:

Storage::withOldFiles()->fake($disk)

Whether users want to keep the uploaded files when testing and make assertions to them.

Storage::fake($disk)

Whether you want to keep the actual behavior.

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Even though I will understand if this PR is not accepted, I would like to see something similar to this in the framework.

@taylorotwell I will appreciate your thoughts on this.

Thanks,

[deleugpn]

keepFiles would be a much better name, imo.

[gocanto]

I really used that name knowing taylor with comes out woth soemthing better. I jist would like to have this behavior in the framework :) though I like that one also :)

[taylorotwell]

What about just a whole new method persistentFake? I don't know why you need a property at all really, and it also creates this state that is left hanging around.

[gocanto]

Ok, that sounds better then. I ll send the pr tonight. Thanks

[gocanto]

Hey @taylorotwell

I made the required changes.

Thanks,