#3493872: Standardize HttpKernel property name across middleware classes
- Rename property
apptohttpKernelin NegotiationMiddleware - Rename property
kerneltohttpKernelin StackedHttpKernel - Update constructor parameter names from
kerneltohttp_kernel - Rename property
apptohttpKernelin AcceptHeaderMiddleware - Rename property
kerneltohttpKernelin TestMiddleware - Update constructor parameter names to match core convention
Closes #3493872
Edited by Heissen Lopez