Merge pull request #1978 from tc39/eliminate-some-false-positives

.../built-ins/Array/prototype/flat/non-object-ctor-throws.js

...t-ins/Array/prototype/flat/null-undefined-input-throws.js

.../prototype/flat/symbol-object-create-null-depth-throws.js

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

...ilt-ins/Array/prototype/flatMap/non-object-ctor-throws.js

...ns/Array/prototype/flatMap/null-undefined-input-throws.js

test/built-ins/Array/prototype/flatMap/proxy-access-count.js

test/built-ins/BigInt/asIntN/bigint-tobigint-errors.js

test/built-ins/BigInt/asIntN/bigint-tobigint-toprimitive.js

test/built-ins/BigInt/asIntN/bits-toindex-errors.js

test/built-ins/BigInt/asIntN/bits-toindex-toprimitive.js

test/built-ins/BigInt/asUintN/bigint-tobigint-errors.js

test/built-ins/BigInt/asUintN/bigint-tobigint-toprimitive.js

test/built-ins/BigInt/asUintN/bits-toindex-errors.js

test/built-ins/BigInt/asUintN/bits-toindex-toprimitive.js

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

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

...nt/prototype/toString/thisbigintvalue-not-valid-throws.js

...Int/prototype/valueOf/this-value-invalid-object-throws.js

.../prototype/valueOf/this-value-invalid-primitive-throws.js