fix put extension short all matched

[paco0x]

Hi @zhangchiqing. Thanks for your great article and repo for explaining MPT of Ethereum.

I found a bug when trying to put on an extension node with matched == len(nibbles). The program will panic with the following case:

func TestPutExtensionAllMatched(t *testing.T) {
    trie := NewTrie()
    trie.Put([]byte{1, 2, 3, 4}, []byte("hello1"))
    trie.Put([]byte{1, 2, 3, 5 << 4}, []byte("hello2"))
    trie.Put([]byte{1, 2, 3}, []byte("world"))

    leaf1 := NewLeafNodeFromNibbles([]Nibble{4}, []byte("hello1"))
    leaf2 := NewLeafNodeFromNibbles([]Nibble{0}, []byte("hello2"))

    branch := NewBranchNode()
    branch.SetBranch(Nibble(0), leaf1)
    branch.SetBranch(Nibble(5), leaf2)
    branch.SetValue([]byte("world"))

    ext := NewExtensionNode([]Nibble{0, 1, 0, 2, 0, 3}, branch)

    require.Equal(t, ext.Hash(), trie.Hash())
}

panic output:

❯ go test -v . -run TestPutExtension
=== RUN   TestPutExtensionShorterAllMatched
--- FAIL: TestPutExtensionShorterAllMatched (0.00s)
panic: runtime error: slice bounds out of range [7:6] [recovered]
        panic: runtime error: slice bounds out of range [7:6]

goroutine 21 [running]:
testing.tRunner.func1.2({0x105348100, 0x140000b42a0})
        /opt/homebrew/Cellar/go/1.19/libexec/src/testing/testing.go:1396 +0x1c8
testing.tRunner.func1()
        /opt/homebrew/Cellar/go/1.19/libexec/src/testing/testing.go:1399 +0x378
panic({0x105348100, 0x140000b42a0})
        /opt/homebrew/Cellar/go/1.19/libexec/src/runtime/panic.go:884 +0x204
merkle-patrica-trie.(*Trie).Put(0x140000496f8, {0x14000049681, 0x3, 0x1050671fc?}, {0x140000a7060, 0x5, 0x5})
        /Users/paco/Projects/ethereum/merkle-patricia-trie/trie.go:169 +0xce0
merkle-patrica-trie.TestPutExtensionShorterAllMatched(0x0?)
        /Users/paco/Projects/ethereum/merkle-patricia-trie/trie_test.go:165 +0x168
testing.tRunner(0x1400013a1a0, 0x105366af0)
        /opt/homebrew/Cellar/go/1.19/libexec/src/testing/testing.go:1446 +0x10c
created by testing.(*T).Run
        /opt/homebrew/Cellar/go/1.19/libexec/src/testing/testing.go:1493 +0x300
FAIL    merkle-patrica-trie     0.719s
FAIL

This PR is trying to fix the above case and also add more test cases to cover put on the extension node.

Trie before put:

                   ┌───────────────────────────┐
                   │                           │
                   │  Extension Node           │
                   │                           │
                   │  Path: [0, 1, 0, 2, 0, 3] │
                   │                           │
                   └────────────┬──────────────┘
                                │
                                │
                                │
                                │
     ┌──────────────────────────┴─────────────────────────────────┐
     │                      Branch Node                           │
     │                                                            │
     │   [0]         ...                  [5]                     │
     └────┼────────────────────────────────┼──────────────────────┘
          │                                │
          │                                │
          │                                │
          │                                │
  ┌───────┴──────────┐           ┌─────────┴─────────┐
  │  Leaf Node       │           │    Leaf Node      │
  │                  │           │                   │
  │  Path: [4]       │           │    Path: [0]      │
  │                  │           │                   │
  │  Value: "hello1" │           │    Value: "hello2"│
  │                  │           │                   │
  └──────────────────┘           └───────────────────┘

After put([]byte{[1, 2, 3]}, "world"):

                   ┌───────────────────────────┐
                   │                           │
                   │  Extension Node           │
                   │                           │
                   │  Path: [0, 1, 0, 2, 0, 3] │
                   │                           │
                   └────────────┬──────────────┘
                                │
                                │
                                │
                                │
     ┌──────────────────────────┴─────────────────────────────────┐
     │                      Branch Node                           │
     │                                                            │
     │   [0]         ...                  [5]    value: "world"   │
     └────┼────────────────────────────────┼──────────────────────┘
          │                                │
          │                                │
          │                                │
          │                                │
  ┌───────┴──────────┐           ┌─────────┴─────────┐
  │  Leaf Node       │           │    Leaf Node      │
  │                  │           │                   │
  │  Path: [4]       │           │    Path: [0]      │
  │                  │           │                   │
  │  Value: "hello1" │           │    Value: "hello2"│
  │                  │           │                   │
  └──────────────────┘           └───────────────────┘

[paco0x]

Done @zhangchiqing