Tests should cover AssignmentExpression with exotic [[Set]] and/or [[DefineOwnProperty]]

[gibson042]

The result of an expression like [].length = "4" must be a string, even though array objects apply special processing to the input that results in the input value being coerced to a uint32 number before it affects the property descriptor. Most implementations get this right, but it's subtle and not covered by test262 AFAICT (and there's an example of getting it wrong at Moddable-OpenSource/moddable#1123 ).

We should probably add some coverage for this case, along with other assignment operators and other receivers (good candidates include proxies, strings, arguments objects, typed arrays, and anything else mentioned in Built-in Exotic Object Internal Methods and Slots).