Autosubmit considers valid email as invalid

Testing the NOTIFY_ON after a bug @apuiggro found, I noticed Autosubmit email validation is incorrect and inconsistent.

If you use local inboxes, for example:

mail:
    NOTIFY_ON_REMOTE_FAIL: True
    NOTIFICATIONS: True
    TO: kinow@localhost

Then autosubmit create will succeed but will print a warning.

$ autosubmit create a030
Autosubmit admin user: eadmin is not set
Autosubmit is running with 4.1.11
Autosubmit admin user: eadmin is not set
Preparing .lock file to avoid multiple instances with same expid.
Using project folder: /home/kinow/autosubmit/a030/proj

Checking configuration files...
Expdef config file is correct
Platforms sections: OK
Jobs sections OK
[WARNING] On Configuration files:
Critical Issues on [Autosubmit] config file:
[mail] invalid e-mail

Loading parameters...

But if you run autosubmit run, then the process crashes, instead of printing a warning (autosubmit create exited with 0, so why is the user not able to run?).

$ autosubmit run a030
Autosubmit admin user: eadmin is not set
Autosubmit is running with 4.1.11

Checking configuration files...
Expdef config file is correct
Platforms sections: OK
Jobs sections OK
 [CRITICAL] On Configuration files:
Critical Issues on [Autosubmit] config file:
[mail] invalid e-mail
 [eCode=7014]
More info at https://autosubmit.readthedocs.io/en/master/troubleshooting/error-codes.html

There are a few RFCs for emails, rfc822, rfc3696, rfc5321, rfc5322, rfc6530… we should probably use something from Python's stdlib, or a good library to validate it, and allow user@domain emails as this is commonly used in some IT environments.