net: clarify UDPConn Read behaviour documentation

[kortschak]

The documentation for UPDConn.Read says that "Read implements the Conn Read method." However, UDP is not stream and Conn is described as "a generic stream-oriented network connection".

It would be nice to be able to know what the characteristics of Read are with respect to packets — whether Read only reads a packet at a time or not — without having to read the source.

See https://groups.google.com/forum/#!topic/golang-nuts/f_s3fGRgAF8

[ruhil6789]

Hi @andybons @kortschak ! I'd like to work on this documentation issue. I'll update the documentation
for UDPConn.Read to clarify that it reads one UDP packet at a time, which differs
from the stream-oriented behavior described in the Conn interface.

I'll add clear documentation explaining:

• That Read reads a single UDP packet per call
• The packet-oriented nature of UDP vs stream-oriented connections
• Any relevant behavior differences users should be aware of

Let me know if there's anything specific I should focus on or if anyone else
is already working on this.

[gopherbot]

Change https://go.dev/cl/732541 mentions this issue: net: clarify UDPConn Read behaviour documentation

[foresto]

Related: #18056