core: move RLP encoding of values to trie

[gballet]

Move the code that serializes an MPT leaf to the MPT tree code itself.

Rationale

The encoding of the leaf in RLP is very much dependent on the format of the tree, and performing the encoding in the state database is causing an abstraction leak: Verkle trees use a different format, and therefore a distinction as to the type of tree has to be made at the database level, which imo should be abstracted to the tree itself.

Consequence

Instead of writing the following in state_object.go's updateTrie:

                if (value == common.Hash{}) {
                      if tr.IsVerkle() {
                              k := trieUtils.GetTreeKeyStorageSlotWithEvaluatedAddress(s.pointEval, new(uint256.Int).SetBytes(key[:]))
                              s.setError(tr.TryDelete(k))
                      } else {
                              s.setError(tr.TryDelete(key[:]))
                      }
                        s.db.StorageDeleted += 1
              } else {
                      // Encoding []byte cannot fail, ok to ignore the error.
                      v, _ = rlp.EncodeToBytes(common.TrimLeftZeroes(value[:]))
                      if !tr.IsVerkle() {
                              s.setError(tr.TryUpdate(key[:], v))
                      } else {
                              // Update the trie, with v as a value
                              s.setError(tr.TryUpdate(key, value[:]))
                      }
             }

the code that supports both MPT and verkle trees become:

                var v []byte
                if (value == common.Hash{}) {
                        s.setError(tr.TryDelete(key[:]))
                        s.db.StorageDeleted += 1
              } else {
                      // Encoding []byte cannot fail, ok to ignore the error.
                      v, _ = rlp.EncodeToBytes(common.TrimLeftZeroes(value[:]))
                      s.setError(tr.TryUpdate(key[:], value[:]))
                      s.db.StorageUpdated += 1
              }

It should have no impact on the root hash of the tree (although there is still an issue with the light client, which is why this PR is still a draft)

Note that rlp.EncodeToBytes is now called twice (in the case of an MPT), in case it ends in the snapshot. This pertains to the snapshot format, which ideally should also be abstracted but doesn't belong in this PR.

[fjl]

This change was merged as part of a different PR, #25458.