RegExp.prototype is not a RegExp, and the algorithm only special-cases
(same-realm) %RegExpPrototype%.

Based on: https://github.com/tc39/test262/blob/44fc8165d54de9c9f0128f70eda56bdcb5dde82c/implementation-contributed/v8/intl/segmenter/segment-iterator-ownPropertyDescriptor.js

Fix wrong expectations of
Intl.RelativeTimeFormat.prototype.formatToParts
Add tests to cover "group", "decimal" and "fraction".

Fixes #1904

Ref: https://github.com/tc39/ecma402/issues/256.

Also cases for double failing resolutions

Also rename test/language/expressions/dynamic-import/assignment-expression/

This reverts commit c49c3567.

Fixes #1342