refactor coverage for flatMap

...-ins/Array/prototype/flatMap/array-like-objects-nested.js

...y/prototype/flatMap/array-like-objects-poisoned-length.js

...Array/prototype/flatMap/array-like-objects-typedarrays.js

test/built-ins/Array/prototype/flatMap/array-like-objects.js

...s/Array/prototype/flatMap/non-callable-argument-throws.js

...ilt-ins/Array/prototype/flatMap/non-object-ctor-throws.js

...ins/Array/prototype/flatMap/this-value-ctor-non-object.js

...type/flatMap/this-value-ctor-object-species-bad-throws.js

...-value-ctor-object-species-custom-ctor-poisoned-throws.js

...ype/flatMap/this-value-ctor-object-species-custom-ctor.js

...Array/prototype/flatMap/this-value-ctor-object-species.js

...ray/prototype/flatMap/this-value-null-undefined-throws.js

test/built-ins/Array/prototype/flatMap/thisArg-argument.js