Serialize/Deserialize slices without length prefix with break-change

[ScarboroughCoral]

Following:

• issue: Serialization without prefix length #202

• pr: Serialize/Deserialize slices without length prefix #208

• Message writer without prefixing a length

• Slice serializer without prefixing a length

• Reading messages that aren't prefixed with a length

• pass test for all the above implementations

[ScarboroughCoral]

I want to fix this issue, but there are something error when testing the code. I think there are some code need to fix in the pb-rs folder, such as pb-rs/src/types.rs