Constrain the size of leios_certificate signers

The maximum length is determined by the maximum LeiosVoterId. As this is
a Word16, the max number of entries is 65535 bits = 8192 bytes

Author: ch1bo

eras/dijkstra/impl/cddl/data/dijkstra.cddl

@@ -895,8 +895,8 @@ auxiliary_data_map =
   )
 
 leios_certificate =
-  [ signers              : bytes           ;bitfield
-  , aggregated_signature : leios_signature
+  [ signers   : bytes .size (0 .. 8192) ;bitfield with up to 65537 entries
+  , signature : leios_signature
   ]
 
 leios_signature = bytes .size 48

eras/dijkstra/impl/cddl/lib/Cardano/Ledger/Dijkstra/HuddleSpec.hs

@@ -59,6 +59,7 @@ import Data.Function ((&))
 import Data.List (nub)
 import Data.Maybe (mapMaybe)
 import Data.Proxy (Proxy (..))
+import Data.String (fromString)
 import Data.Text ()
 import Data.Text qualified as T
 import Data.Word (Word16, Word64)
@@ -1004,9 +1005,12 @@ instance HuddleRule "leios_certificate" DijkstraEra where
   huddleRuleNamed pname era =
     pname
       =.= arr
-        [ "signers" ==> VBytes & comment "bitfield"
-        , "aggregated_signature" ==> huddleRule @"leios_signature" era
+        [ "signers" ==> VBytes `sized` (0 :: Word64, maxSigners `div` 8 :: Word64)
+            & comment (fromString $ "bitfield with up to " <> show maxSigners <> " entries")
+        , "signature" ==> huddleRule @"leios_signature" era
         ]
+    where
+      maxSigners = 2 ^ (16 :: Word) + 1
 
 instance HuddleRule "leios_signature" DijkstraEra where
   huddleRuleNamed pname _era =