HashMap: add info to docs about random seed quality
HashMap: add info to docs about random seed quality

The random functions that HashMap use make no guarantees about the
quality of random data so this documents that to the user so that they
are aware. This was brought about by the change to the Linux random code
to not block until the urandom pool was initialized to avoid users of
crates that internally use HashMap being caught unaware and having their
application block until the urandom pool is initialized.

Signed-off-by: Doug Goldstein <8172f793ca553050868d487fd13b508d19cae503@cardoe.com>

graydon/rust,aidancully/rust,GBGamer/rust,graydon/rust,GBGamer/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,GBGamer/rust,GBGamer/rust,graydon/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,GBGamer/rust,GBGamer/rust,aidancully/rust