Optimized reading payload

[techraed]

Instead of reading the whole payload and having issue with staticness and move semantics, we can read the payload partially using the demanded parts in corresponding parts of the code.
The received payload has encoded contract (SERVICE_ROUTE-METHOD-PARAMS). The params part can be the heaviest, while the first two are pretty small. What's more we know in advance the size of the first two. So we can just read the first two into arrays with statically defined sizes and use it in-place. But read params only when demanded.
This will allow to avoid clones from the #939