feat: http 'source_interface' parameter

[raboof]

What this PR does / Which issue(s) does the PR fix:

Add a 'source_interface' parameter to the 'http' probe

Does this PR introduce a user-facing change?

[FEATURE] allow restricting the HTTP probe to a given network interface

Sadly I didn't see a clear way to meaningfully test this feature.

Checklist

• [ ] Tests updated
• [x] Documentation added
• [x] CHANGELOG added in release-notes section of PR Desc.