Move iterable checks from type_cast_value to __init__

[davidism]

Both the errors raised in type_cast_value should be in __init__ instead. The composite error should be removed from type_cast_value, it makes no sense at runtime. Both places that value is iterated in type_cast_value should raise a BadParameter error instead of TypeError.

Originally posted by @davidism in #1805 (comment)

[davidism]

@Saif807380 want to work on this?

[Saif807380]

Sure. I'll have a go at it.