Move tests for Array `length` to a proper folder

test/built-ins/Array/length/15.4.5.1-3.d-1.js

test/built-ins/Array/length/15.4.5.1-3.d-2.js

test/built-ins/Array/length/15.4.5.1-3.d-3.js

test/built-ins/Array/length/S15.4.4_A1.3_T1.js

test/built-ins/Array/length/S15.4.5.1_A1.1_T1.js

test/built-ins/Array/length/S15.4.5.1_A1.1_T2.js

test/built-ins/Array/length/S15.4.5.1_A1.2_T1.js

test/built-ins/Array/length/S15.4.5.1_A1.2_T3.js

test/built-ins/Array/length/S15.4.5.1_A1.3_T1.js

test/built-ins/Array/length/S15.4.5.1_A1.3_T2.js

test/built-ins/Array/length/S15.4.5.2_A3_T4.js

...ins/Array/length/define-own-prop-length-overflow-realm.js