The --new-vault-password-file option works the same as
--vault-password-file but applies only to rekeying (when
--vault-password-file sets the old password). Also update the manpage
to document these options more fully.

Support for ANSIBLE_HOSTS is faded out, see commit
c7325454, therefore do not mention it in
the man pages.

Fixes #9574

Fixes #9758

Note: the man page needs to be rebuilt.

Fixes #6471

Partially resolves #6471

raise errors when omitted, updated changelog with new modules.

Same doc-typo (confirmed) as https://github.com/ansible/ansible/pull/4759

--remote-user  *should be*  --user

--remote-user= does not work:
 ansible: error: no such option: --remote-user

--user= does. Updating docs

Thi permit to simplify the command line to use by using
a sensible default, and so reduce the number of incorrect
possible choices and setup needed. Among potential
incorrect choices is using a fixed directory in /tmp, which
could be problematic with a setup whose access is not
properly restricted.