Use TLS 1.3 instead of TLS1.2

See merge request bortzmeyer/homer!33

Requires OpenSSL >= 1.1.1 and pyOpenSSL >= 21.0.0

Rename to Remoh

Closes #32

Due to possible legal issues with the use of «Homer» to refer to the
project and the tool, it has been decided to change the name into Remoh.

[DoT] Catch closed connection

See merge request bortzmeyer/homer!30

Calculate the elapsed time per query based on the number of finished
queries and not the number of wanted queries.

Based on OpenSSL manual and pyOpenSSL documentation, a closed connection
raises an error SSL_ERROR_ZERO_RETURN which raises a ZeroReturnError
exception.
See <https://www.openssl.org/docs/man1.1.0/man3/SSL_get_error.html> and
<https://www.pyopenssl.org/en/stable/api/ssl.html#OpenSSL.SSL.ZeroReturnError>

Do not exit on error with --check

See merge request bortzmeyer/homer!28

The error() function should be used to diplay an error message. If the
program should exit after printing the error message, use
error_and_exit() function instead.

Improve --check

* refactor
* better output (number of resolved IPs, error after test status)
* new mandatory level : `nocrash`

See merge request bortzmeyer/homer!27