Optimize VConstr bounds check in CEK machine (#7479)

Simplify the type conversion in VConstr index validation by
eliminating unnecessary intermediate conversion through Integer.

Changed from:
  fromIntegral @_ @integer i > fromIntegral @int @integer maxBound
To:
  i > fromIntegral @int @Word64 maxBound

Since i is already Word64, we can directly compare it to maxBound
converted to Word64, which is more efficient and clearer.

Also updated Note [Integral types as Integer] to clarify that all
non-64-bit systems (not just 32-bit) are banned for node deployment.

Fixes #7478

Author: Unisay

plutus-core/plutus-core/src/PlutusCore/Default/Universe.hs

@@ -489,8 +489,8 @@ So, what to do? We adopt the following strategy:
 - We allow lifting/unlifting 'Int' via 'Int64' and 'Word' via 'Word64', constraining the conversion
   between them to 64-bit architectures where this conversion is safe.
 
-Doing this effectively bans builds on 32-bit systems, but that's fine, since we don't care about
-supporting 32-bit systems anyway, and this way any attempts to build on them will fail fast.
+Doing this effectively bans builds on all non-64-bit systems, which is acceptable since 64-bit
+systems are required for node deployment, and this way any attempts to build on them will fail fast.
 
 We used to use newtype- and via-deriving for implementations of relevant instances, but at some
 point GHC stopped attaching @INLINE@ annotations to those causing the GHC Core for builtins to have

plutus-core/untyped-plutus-core/src/UntypedPlutusCore/Evaluation/Machine/Cek/Internal.hs

@@ -927,7 +927,7 @@ enterComputeCek = computeCek
       -- Word64 value wraps to -1 as an Int64. So you can't wrap around enough to get an
       -- "apparently good" value.
       (VConstr i _)
-        | fromIntegral @_ @Integer i > fromIntegral @Int @Integer maxBound ->
+        | i > fromIntegral @Int @Word64 maxBound ->
             throwErrorDischarged (StructuralError (MissingCaseBranchMachineError i)) e
       -- Otherwise, we can safely convert the index to an Int and use it.
       (VConstr i args) -> case (V.!?) cs (fromIntegral i) of