Add mention of join() to the section of the manual about strings

This is one of the very useful functions which can be hard to find,
and very similar to repeat().

(cherry picked from commit ef0e5571cc7af40f66ef7226b6a02065cf4ce2f0)
ref PR #9426
String docs: start to add crosslinks between manual and stdlib

(cherry picked from commit 6655241e5fe65f876c8039f05964e96ba5ff7f30)
Update networking-and-streams.rst

`read(stream, array)` is deprecated in favor of read!()
(cherry picked from commit 6d57cdc5b601884cf68ae334939596fc219a083d)
ref PR #9383