Refactor tests for the BigInt construtor

test/built-ins/BigInt/asUintN.js

test/built-ins/BigInt/constructor-prototype.js

test/built-ins/BigInt/infinity-throws-rangeerror.js

test/built-ins/BigInt/nan-throws-rangeerror.js

test/built-ins/BigInt/negative-infinity-throws.rangeerror.js

test/built-ins/BigInt/new-target-throws.js

test/built-ins/BigInt/non-integer-rangeerror.js

test/built-ins/BigInt/out-of-bounds-integer-rangeerror.js

test/built-ins/BigInt/parseInt/parseInt.js

test/built-ins/BigInt/prop-desc.js

test/built-ins/BigInt/proto.js

test/built-ins/BigInt/prototype/prop-desc.js

test/built-ins/BigInt/prototype/proto.js

test/built-ins/BigInt/prototype/prototype-is-object.js

test/built-ins/BigInt/prototype/toString.js

test/language/expressions/addition/bigint-to-string.js

.../language/expressions/addition/coerce-bigint-to-string.js

.../language/expressions/division/bigint-complex-infinity.js

test/language/expressions/division/bigint.js

test/language/expressions/does-not-equals/bigint.js