Metasploit::Concern.run and shared example

[MSP-9895](https://jira.tor.rapid7.com/secure/RapidBoard.jspa?rapidView=84&view=detail&selectedIssue=MSP-9895)

I forgot to include the `ActiveSupport.run_load_hooks(<name>, self)` in some gems.  To prevent this in the future, there is now the `'Metasploit::Cocern.run'` shared example which will check that `ActiveSupport.run_load_hooks` is called with the correct name and base (`self` for the `described_class`).  As can be seen, I also added `Metasploit::Concern.run`, which only has to be called with `self` from the bottom of the class body and it will calculate the correct name to call `ActiveSupport.run_load_hooks` with.