ml tests for dga detection

[YellowMan02]

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• I have signed the ntop Contributor License Agreement at https://github.com/ntop/legal/blob/main/individual-contributor-licence-agreement.md
• I have read the contributing guidelines at https://github.com/ntop/nDPI/blob/dev/CONTRIBUTING.md
• I have updated the documentation (in doc/) to reflect the changes made (if applicable)

Describe changes:
added tests with 2 different machine learning models to address dga detection.

[sonarcloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[utoni]

Thanks for the PR!
Could you please add the files to EXTRA_DIST so they will be included when running make dist. :)