CLN: Specialize assert_(np.array_equal(...))

Work on #6175. This is the third (and final) "half" of the work started in #6368.
API/CLN: add in common operations to Series/Index, refactored as a OpsMixin
         (GH4551, GH4056, GH5519)
Merge pull request #6380 from jreback/common_ops

API/CLN: add in common operations to Series/Index, refactored as a OpsMixin
Merge pull request #6387 from bwignall/assert_6175_arrayequal_3

CLN: Specialize assert_(np.array_equal(...))
CLN: Change assert_(a is [not] b) to specialized forms

Work on #6175. Changes instances of assert_(a is [not] b) to specialized assertIs[Not](a, b).
Merge pull request #6392 from bwignall/assert_6175_isisnot

CLN: Change assert_(a is [not] b) to specialized forms