Introduce 'Never' type as a safe alternative to always None options

Unfortunately, as documented in:

  https://github.com/IntersectMBO/cardano-ledger/issues/4571

  Some Option fields in the script context certificates are going to
  remain set to None, at least until the next Hard fork. There's a risk
  that people permanently lock their funds if they expect deposits on
  registration credentials to ever be `Some`.

  So, we introduce a special type that emulate an `Option` that can only
  ever be `None`. We call it `Never` and it is the first type of this
  kind (i.e. with constructors indexes not starting at 0).

examples/acceptance_tests/script_context/v3/aiken.lock

@@ -13,4 +13,4 @@ requirements = []
 source = "github"
 
 [etags]
-"aiken-lang/stdlib@v2" = [{ secs_since_epoch = 1724491200, nanos_since_epoch = 427525000 }, "cdbbce58b61deb385e7ea787a2e0fc2dc8fe94db9999e0e6275bc9c70e5796be"]
+"aiken-lang/stdlib@v2" = [{ secs_since_epoch = 1724760716, nanos_since_epoch = 700202000 }, "cdbbce58b61deb385e7ea787a2e0fc2dc8fe94db9999e0e6275bc9c70e5796be"]

examples/acceptance_tests/script_context/v3/validators/certificates.ak

@@ -71,7 +71,7 @@ validator purposes {
       Some(
         RegisterCredential {
           credential: VerificationKey(only0s),
-          deposit: Some(3_000_000),
+          deposit: None,
         },
       ) == list.at(certificates, 5)
 
@@ -79,7 +79,7 @@ validator purposes {
       Some(
         UnregisterCredential {
           credential: VerificationKey(only0s),
-          refund: Some(3_000_000),
+          refund: None,
         },
       ) == list.at(certificates, 6)