refactor(cardano): align PParms field names with db-sync naming conventions

[ricomiles]

This PR updates the field names of the protocol parameters to align with the naming conventions used in db-sync.

Most of these changes are straightforward. However, one notable example is the max_execution_units_per_transaction parameter. In the current spec, this parameter is defined as:
ExUnits max_execution_units_per_transaction

where ExUnits is defined as:

ExUnits {
  uint64 steps = 1;
  uint64 memory = 2;
}

In db-sync, there isn’t a single field corresponding to max_execution_units_per_transaction. Instead, db-sync uses separate fields: max_tx_ex_steps and max_tx_ex_mem. To address this, we’ve chosen to rename max_execution_units_per_transaction to max_tx_ex while retaining the ExUnits type and just chaning the name from memory to mem. This approach kind of matches the naming convention in db-sync without significantly altering the spec.

An alternative would be to remove the ExUnits type entirely and define max_tx_ex_steps and max_tx_ex_mem as separate fields. However, this would be a more substantial change to the structure.

This also applies to the following parameters:

• max_execution_units_per_block
• prices