Update tests to use assert.throws
Add test for throwing on bad `this`

Fixes @caitp's review comment at https://codereview.chromium.org/771863002/diff/60001/test/mjsunit/harmony/array-includes-to-object.js.
Add test for this value in getter on a number

Addresses @arv's review comment at https://codereview.chromium.org/771863002/diff/60001/test/mjsunit/harmony/array-includes-to-object.js.