Extract proposal new from shared nested imageable specs to system specs

Make `path`, `fill_resource_method_name`, `submit_button`, and
`imageable_success_notice` dynamic based on the factory.

Also adjusted the user. The proposals no longer require the user to be an
administrator but do require them to be a level 2 user.

Note that we are adding the Style/CaseLikeIf rubocop rule.

.rubocop.yml

@@ -694,6 +694,9 @@ Style/ArrayIntersect:
 Style/BlockDelimiters:
   Enabled: true
 
+Style/CaseLikeIf:
+  Enabled: true
+
 Style/ClassCheck:
   Enabled: true