Closes#83
This PR aims to move all of Valence's networking code to the new
`valence_protocol` crate. Anything not specific to valence is going in
the new crate. It also redesigns the way packets are defined and makes a
huge number of small additions and improvements. It should be much
easier to see where code is supposed to go from now on.
`valence_protocol` is a new library which enables interactions with
Minecraft's protocol. It is completely decoupled from valence and can be
used to build new clients, servers, tools, etc.
There are two additions that will help with #5 especially:
- It is now easy to define new packets or modifications of existing
packets. Not all packets need to be bidirectional.
- The `CachedEncode` type has been created. This is used to safely cache
redundant calls to `Encode::encode`.
This change was made to make it easier for invariants to be upheld. When
the spatial partition is added, we can ensure that changes to entities
are immediately reflected in the partition. Additionally, chunks being
shared between worlds was a leaky abstraction to begin with and is now
removed. A method in `Config` is now necessary to determine what world a
client should join.
Along with this, most mutable references have been wrapped in a newtype
to ensure that `mem::swap` cannot be used on them, which would break
invariants. This is analogous to `Pin<&mut T>`. The reason we can't use
Pin directly is because it would require unnecessary unsafe code
within the library.
