Atomics: refactor atomicsHelper.js to extend $262.agent.*

harness/atomicsHelper.js

test/built-ins/Atomics/isLockFree/expected-return-value.js

.../built-ins/Atomics/wait/bigint/false-for-timeout-agent.js

test/built-ins/Atomics/wait/bigint/good-views.js

test/built-ins/Atomics/wait/bigint/nan-for-timeout.js

test/built-ins/Atomics/wait/bigint/negative-timeout-agent.js

...ns/Atomics/wait/bigint/no-spurious-wakeup-no-operation.js

...uilt-ins/Atomics/wait/bigint/no-spurious-wakeup-on-add.js

...uilt-ins/Atomics/wait/bigint/no-spurious-wakeup-on-and.js

...mics/wait/bigint/no-spurious-wakeup-on-compareExchange.js

...ins/Atomics/wait/bigint/no-spurious-wakeup-on-exchange.js

...built-ins/Atomics/wait/bigint/no-spurious-wakeup-on-or.js

...lt-ins/Atomics/wait/bigint/no-spurious-wakeup-on-store.js

...uilt-ins/Atomics/wait/bigint/no-spurious-wakeup-on-sub.js

...uilt-ins/Atomics/wait/bigint/no-spurious-wakeup-on-xor.js

test/built-ins/Atomics/wait/bigint/value-not-equal.js

...mics/wait/bigint/waiterlist-block-indexedposition-wake.js

...ics/wait/bigint/waiterlist-order-of-operations-is-fifo.js

...built-ins/Atomics/wait/bigint/was-woken-before-timeout.js

test/built-ins/Atomics/wait/false-for-timeout-agent.js