Rust add snmp 02

[chifflier]

Make sure these boxes are signed before submitting your Pull Request -- thank you.

• I have read the contributing guide lines at https://redmine.openinfosecfoundation.org/projects/suricata/wiki/Contributing
• I have signed the Open Information Security Foundation contribution agreement at https://suricata-ids.org/about/contribution-agreement/
• I have updated the user guide (in doc/userguide/) to reflect the changes made (if applicable)

Link to redmine ticket:
https://redmine.openinfosecfoundation.org/issues/2738

This is an update of #3581

Describe changes (since last PR):

• Upgrade to nom4 (inner parser crate was also updated)
• Rebase to match changes
• Rename keywords (snmp_version -> snmp.version, etc.)

There will also be a matching suricata-verify pull request with test files.

[chifflier]

Thanks, all requested changes merged.
Closing pr, superseded by #3883