Load edited file after `edit` command

[okuramasafumi]

We have edit command which invokes a text editor from IRB. This is convenient when we launch IRB with bin/console command so that we can modify a bit of code and see the change.
However, when we exit the editor and come back to IRB, the edited file is not loaded automatically. This provides virtually similar experience to open the editor separately, and we can improve this experience by loading the file after edit.

As a reference, Pry's edit command supports "reload" feature that's enabled by default.
https://github.com/pry/pry/blob/master/lib/pry/commands/edit.rb

So my suggestion is to add auto-load option to edit command first with false as default. Then make that option true as default from the next major version of IRB.
When the option is true, we will simply load that file in IRB.