Dynamic Fees - Codec upgrades for dynamic fees - TO BE CLOSED

[abi87]

Replaced by #2699

Why this should be merged

The way we plan to meter transactions complexity and fees requires two things from our codec:

1. Codec must be able to size incomplete structs, even if it is not able to marshal them. Incomplete structs are structs with nil pointers or ni interfaces as members. Incomplete structs happens when we are building the tx and we need to meter a partially filled tx to understand whether another utxos must be burned or not
2. Struct size must be additive wrt to structs members. This ensures that size of a complete structs (all member filled so that it can be marshalled) is the sum of the partially filled struct and its members. This is already true for our codec, so we just need to introduce UTs to show it

How this works

Modified codec size and added UTs to show the required invariants

How this was tested

CI + extra UTs