some quick fixes for Array.prototype.{flat,flatMap} tests

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

test/built-ins/Array/prototype/flat/length.js

test/built-ins/Array/prototype/flat/name.js

...rray/prototype/flat/non-numeric-depth-should-not-throw.js

.../built-ins/Array/prototype/flat/non-object-ctor-throws.js

test/built-ins/Array/prototype/flat/prop-desc.js

test/built-ins/Array/prototype/flat/proxy-access-count.js

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

test/built-ins/Array/prototype/flatMap/length.js

test/built-ins/Array/prototype/flatMap/name.js

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

test/built-ins/Array/prototype/flatMap/prop-desc.js

test/built-ins/Array/prototype/flatMap/proxy-access-count.js