Add features tags for Atomics and SharedArrayBuffer (#1494)

test/built-ins/Atomics/Symbol.toStringTag.js

test/built-ins/Atomics/add/descriptor.js

test/built-ins/Atomics/add/length.js

test/built-ins/Atomics/add/name.js

test/built-ins/Atomics/add/nonshared-int-views.js

test/built-ins/Atomics/add/shared-nonint-views.js

test/built-ins/Atomics/and/descriptor.js

test/built-ins/Atomics/and/length.js

test/built-ins/Atomics/and/name.js

test/built-ins/Atomics/and/nonshared-int-views.js

test/built-ins/Atomics/and/shared-nonint-views.js

test/built-ins/Atomics/compareExchange/descriptor.js

test/built-ins/Atomics/compareExchange/length.js

test/built-ins/Atomics/compareExchange/name.js

.../built-ins/Atomics/compareExchange/nonshared-int-views.js

.../built-ins/Atomics/compareExchange/shared-nonint-views.js

test/built-ins/Atomics/exchange/descriptor.js

test/built-ins/Atomics/exchange/length.js

test/built-ins/Atomics/exchange/name.js

test/built-ins/Atomics/exchange/nonshared-int-views.js