Don't mutate the Base settings by merge!ing the given value
Fix order dependent tests

Restore default ActiveSupport::XmlMini.backend after tests
Be sure to restore the default I18n.locale after changed its value in a test
Refactor handling of action normalization

Reference:
Bloody mess internals
http://gusiev.com/slides/rails_contribution/static/#40
Excluding action_view/vendor in API [ci skip]
Removed excluding vendor from API doc [ci skip]

These folder not exists in system
Merge pull request #11611 from arunagw/api-generation-av

Excluding action_view/vendor in API[ci skip]
Removed an unnecessary loop - it kills performance on large texts.
if! -> unless