Fix various bugs in test cases (#1988)

src/class-elements/prod-private-async-method.case

...s/Array/prototype/flatMap/non-callable-argument-throws.js

...lect/ownKeys/return-on-corresponding-order-large-index.js

test/intl402/NumberFormat/currencyDisplay-unit.js

test/intl402/NumberFormat/style-unit.js

test/intl402/Segmenter/iterator/following.js

test/intl402/Segmenter/iterator/granularity.js

test/intl402/Segmenter/iterator/preceding.js

test/intl402/Segmenter/prototype/segment/segment-line.js

test/intl402/Segmenter/prototype/segment/segment-sentence.js

test/intl402/Segmenter/prototype/segment/segment-word.js

...ssions/class/private-methods/prod-private-async-method.js

...ements/class/private-methods/prod-private-async-method.js