fix: Reuse buffer in stream reader

[MikeGoldsmith]

Which problem is this PR solving?

After further investigation using profiling, we still see high in-use objects in memory that creep up over an extended time. It looks like each call to bufio.NewReader allocates a new 4mb byte[] which is never cleaned up correctly.

This PR moves the bufio.Reader to the the reader struct and reuses it when processing packet data.

Short description of the changes

• Add bufio.Reader to tcpReader and initalise during NewTcpReader
• Reuse the buffered reader when processing new packet data by calling Reset with the new data.

Note: We do not cache the io.Reader as this doesn't hold onto the underlying []byte and is cleaned up as expected. See the image above for bytes.NewReader.

How to verify that this has the expected result

Memory consumption over an extended period is more stable and does not incrementally creep up.

[robbkidd]

[JamieDanielson]