Fix all properties implemented as a data property where the spec requires an accessor property

[p-bakker]

On several built-ins properties are implemented ad data properties, while the spec calls for accessor properties

Currently only the size property for Set and Map is implemented properly (through NativeMap/Set.init(...))

Affects:

• TypedArray.buffer/byteLength/byteOffset
• DataView.buffer/byteLength/byteOffset
• ArrayBuffer.byteLength
• Regex.flag/global/multiline/ignoreCase
• Symbol.description (see Implement ES2019 Symbol.prototype.description #962)
• All @@species properties (Not yet implemented, part of ES2015 Classes and inheritance #835)

All locations in the spec can be found by searching the spec for the text is an accessor property

[rbri]

Will have a look....