Add new CSP methods to developer changelog #18198

Description:

See #18197 which should be merged in Matomo 4.6.0 before this is merged.

Review

• [ ] Functional review done
• [ ] Potential edge cases thought about (behavior of the code with strange input, with strange internal state or possible interactions with other Matomo subsystems)
• [ ] Usability review done (is anything maybe unclear or think about anything that would cause people to reach out to support)
• [ ] Security review done
• [ ] Wording review done
• [ ] Code review done
• [ ] Tests were added if useful/possible
• [ ] Reviewed for breaking changes
• [ ] Developer changelog updated if needed
• [ ] Documentation added if needed
• [ ] Existing documentation updated if needed

Do we also need to remove the report-only mode @justinvelluppillai ?

And we'll need to make sure to get https://github.com/matomo-org/plugin-AnonymousPiwikUsageMeasurement/issues/59 done before removing the report-only mode and release a new version cc @AltamashShaikh maybe could be good to look at that issue in the next days

@tsteur yes that's done in here: https://github.com/matomo-org/matomo/pull/18197