Upgrade factory_girl to factory_bot
Upkeep for our test suite, from :
Replace all uses of static attributes in factories with dynamic attributes, required for v4.11.0 onwards.
Install the gem factory_bot instead of its now-deprecated predecessor factory_girl.
Update the pickle gem, since otherwise creating users in cucumber features breaks.
Update the bundled major version of factory_bot to 5.x.
How to test: none, automated.