Use Serializer::collect_str to serialize output of Display

[paolobarbolini]

Serializer::collect_str is exactly the same as doing Serializer::serialize_str(&thing_to_serialize.to_string()), but some Serializer implementations, for example the serde_json Serializer, avoid the allocation made by ToString and serialize the item in place

[krisprice]

Hi @paolobarbolini - so this is just an efficiency improvement? Functionally nothing changes right? I'll include it on the next release in that case, sorry I missed it this time around.

[paolobarbolini]

Yeah it's only an efficiency improvement and nothing changes in the funtcionally