On constant missing Ruby call `#inspect` on the receiver to build
the error message.

For instance, the error message for `Foo::Bar` will be `"#{Foo.inspect}::Bar"`.

And since Active Record override the model classes inspect method, this
breaks `missing_name` assumptions.

Until now it worked because missing_name was only called on errors
raised by the classic autoloader, and the classic autoloader calls
`#name` to build its error message.