ref(interfaces): Update the Http interface (request)

[jan-auer]

Changes normalization of the Http interface (request):

• Content type inference still happens, but the body is left as it was ingested.
• Query strings are now stored as pair lists internally, not as string.

[jan-auer]

I still want to change the create_sample_event code for tests so that it doesn't add arbitrary interfaces to the sample JSONs. Just need to verify what implications this might have to the seed functionality in prod.

[jan-auer]

We will split this up in two PRs to further minimize the impact. Query string changes are good to go, the body parsing change needs one final review.

[untitaker]

#11414 #11413 supersede this