remove ContentTypes stuff, fix bad redirect after adapter change

[emmachughes]

Discovered while working on #2768

CA has a handful of classes that implement ContentTypesInterface. These are only used by /create/{contenttype?} / ContentController, which only gathers some data and then tries to render a non-existent view. This removes that route, controller, all the implementations of ContentTypesInterface, and the translations used exclusively by them.

Since the adapter switching controller redirects to that route (and results in an error), it is changed to return nothing, and the JS code is altered to just reload the page.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 70.80%. Comparing base (0b1b330) to head (1424257).
Report is 1 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master    #2771      +/-   ##
============================================
+ Coverage     69.67%   70.80%   +1.12%     
+ Complexity     2700     2671      -29     
============================================
  Files           272      263       -9     
  Lines         11536    11353     -183     
============================================
  Hits           8038     8038              
+ Misses         3498     3315     -183     

Components	Coverage Δ
contentauthor	70.80% <ø> (+1.12%)	⬆️