Add anonymise-donations CLI command

[Abban]

Sometimes we need to run the anonymiser in order to
investigate issues in our application. This adds a
command to allow it from the developer environment.

Ticket: https://phabricator.wikimedia.org/T400323

[gbirke]

We deploy the cli directory together with the rest of the application, which means that theoretically we could accidentally run this in production.

I'm not sure about the use case scenario for this. If you need anonymised donations to test something on a confirmation page, we should rather have a command that inserts test data (reusing fixtures from teh donation bounded context). If you want to test anonymization code, you could insert the fixtures in the FOC (it already has a command to insert them) and run the regular anonymization command there.

If we can come up with a good scenario why we need this, we should add an APP_ENV check to the command and only allow this for dev.