Make public deserialize methods deser_v2 & deser_v2_compressed

[EliSnow]

Specifically I'm interested in calling the deser_v2 method directly. My motivation is I'm using hdrhistogram in a WASM module where I only need to deserialize uncompressed histograms. By using the deserialize method the compiler can not statically determine that I will not be deserializing compressed histograms and flate2 gets included in my WASM.

I only included deser_v2_compressed in the title because I figured if you make public one of them then perhaps it makes sense to do both(??).

[jonhoo]

I think @marshallpierce has more insight into what else we might want to do before making these public. Might be fine to just mark them pub, but want to check with him first.

[marshallpierce]

Interesting. It's a bit of an abstraction-layer mangling to simply mark them pub, but I definitely want to support WASM use cases!

Anyone have thoughts on other ways to do this, perhaps by making a trait to represent derserialization strategies?

[EliSnow]

There are two structs for serializing: V2Serializer and V2DeflateSerializer. Would it make sense to follow this pattern for deserializing? V2Deserializer and V2DeflateDeserializer? The only hickup I see is that the two serializers implement a common trait Serializer and if we wanted the deserializers to implement a common trait, it would have to be named something other than Deserializer since that's taken by the struct.