Fix various typos, repeated words, align some spelling to LDP.

Partially revamped from #16712
- fall thru -> fall through
- time stamp -> timestamp
- host name -> hostname
- ipv6 -> IPv6

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/19059)