refactor: moving hash functions to relevant classes (#4551)

Fixes #4411
Partially addresses #4410 (will finish that in a separate PR since this
one is already huge)

\+ renamed `abis.ts` in circuits.js as `hash.ts`
\+ nuked useless `secrets.ts` in `aztec.js`
\+ ordered the Noir struct length constants since they were all over the
place
\+ added more length checks to `toFields()` methods (we don't need the
length tests when these checks are present - serialization ones are
enough)

aztec/src/context/inputs/private_context_inputs.nr

@@ -1,4 +1,7 @@
-use dep::protocol_types::{abis::call_context::CallContext, contrakt::deployment_data::ContractDeploymentData, header::Header};
+use dep::protocol_types::{
+    abis::call_context::CallContext, contrakt::contract_deployment_data::ContractDeploymentData,
+    header::Header
+};
 use crate::context::globals::private_global_variables::PrivateGlobalVariables;
 
 // PrivateContextInputs are expected to be provided to each private function