Fix property parsing when a property contains a struct

[knutwalker]

Properties are parsed lazily by deserializing the data into an IgnoredAny
and then returning the bytes that have been read.

We do parse structs as an enum in order to emit the struct tag as enum tag.
The IgnoredAny then deserializes a newtype enum variant, expecting a single item.
The VariantAccess impl for the packstream deserializer would then only emit the next field in the struct, introducing the bug.
The fix is to emit all fields when the list of items is from a struct and we are parsing properties.

Fixes #209