go: Define a bytePool for TRichTransport

Client: go

TBinaryProtocol and TCompactProtocol (and as an extension,
THeaderProtocol) use TRichTransport's ReadByte/WriteByte functions a lot
under the hood, and in some extreme cases those ReadByte/WriteByte calls
can generate a lot of allocations for the byte they used.

Use a resource pool to help reduce the allocations.