Synflood protection v0.10

[regit]

Draft PR containing the code that will be presented at Suricon 2025

Contribution style:

• [x] I have read the contributing guide lines at https://docs.suricata.io/en/latest/devguide/contributing/contribution-process.html

Our Contribution agreements:

• [x] I have signed the Open Information Security Foundation contribution agreement at https://suricata.io/about/contribution-agreement/ (note: this is only required once)

Changes (if applicable):

• [ ] I have updated the User Guide (in doc/userguide/) to reflect the changes made
• [x] I have updated the JSON schema (in etc/schema.json) to reflect all logging changes (including schema descriptions)
• [ ] I have created a ticket at https://redmine.openinfosecfoundation.org/projects/suricata/issues

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

Describe changes:

• Update simple hash
• Implement syn flood protection

[victorjulien]

As discussed in person at Suricon, I think the first step is to do profiling and analysis of the existing code under these conditions. I'd like to understand better where the bottlenecks are.