ovpn_reorganize_encryption: Integrate HMAC selection to global section

ovpn_reorganize_encryption: Integrate HMAC selection to global section

Fixes: #12009 and #11824
- Since HMACs will be used in any configuration it is better placed in the global menu.
- Adapted global section to advanced and marked sections with a headline for better overview.
- Deleted old headline in advanced section cause it is not needed anymore.
- Added check if settings do not includes 'DAUTH', if possible SHA512 will be used and written to settings file.
    Old configurations with SHA1 will be untouched.

Signed-off-by: Erik Kapfer <ummeegge@ipfire.org>
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>