Address review comments from Enterlist PR

eth/p2p/discoveryv5/enr.nim

@@ -229,7 +229,7 @@ proc fromBytesAux(r: var Record): bool =
     return false
 
   # We already know we are working with a list
-  discard rlp.enterList()
+  doAssert rlp.enterList()
   rlp.skipElem() # Skip signature
 
   r.seqNum = rlp.read(uint64)

eth/p2p/rlpx_protocols/waku_protocol.nim

@@ -153,11 +153,9 @@ proc read*(rlp: var Rlp, T: typedesc[StatusOptions]): T =
 
   let sz = rlp.listLen()
   # We already know that we are working with a list
-  discard rlp.enterList()
+  doAssert rlp.enterList()
   for i in 0 ..< sz:
-    if not rlp.enterList():
-      raise newException(RlpTypeMismatch,
-        "List expected, but the source RLP is not a list.")
+    rlp.tryEnterList()
 
     var k: KeyKind
     try:

eth/trie/hexary.nim

@@ -387,7 +387,7 @@ proc replaceValue(data: Rlp, key: NibblesRange, value: BytesRange): Bytes =
   # XXX: This can be optimized to a direct bitwise copy of the source RLP
   var iter = data
   # We already know that we are working with a list
-  discard iter.enterList()
+  doAssert iter.enterList()
   for i in 0 ..< 16:
     r.append iter
     iter.skipElem
@@ -513,7 +513,7 @@ proc deleteAt(self: var HexaryTrie;
         var rlpRes = initRlpList(17)
         var iter = origRlp
         # We already know that we are working with a list
-        discard iter.enterList
+        doAssert iter.enterList
         for i in 0 ..< 16:
           rlpRes.append iter
           iter.skipElem

tests/rlp/test_api_usage.nim

@@ -102,7 +102,7 @@ test "encode and decode lists":
   var list = rlpFromBytes encodeList(rlp.listELem(1), rlp.listELem(0)).toRange
 
   # test that iteration with enterList/skipElem works as expected
-  discard list.enterList # We alreay know that we are working with a list
+  doAssert list.enterList # We already know that we are working with a list
   check list.toString == "Lorem ipsum dolor sit amet"
   list.skipElem