util: throw if unreachable TypedArray checking code is reached

If a comparison code path that is supposed to be unreachable is reached,
throw. Add a c8 comment to ignore coverage for the line, as it
should be unreachable.

PR-URL: https://github.com/nodejs/node/pull/31737
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

lib/internal/util/comparisons.js

@@ -147,7 +147,11 @@ function isIdenticalTypedArrayType(a, b) {
       return check(b);
     }
   }
-  return false;
+  /* c8 ignore next */
+  assert.fail(
+    `Unknown TypedArray type checking ${a[SymbolToStringTag]} ${a}\n` +
+    `and ${b[SymbolToStringTag]} ${b}`
+  );
 }
 
 // Notes: Type tags are historical [[Class]] properties that can be set by