Implement stacktrie to improve RLP/hashing performance

[trinhdn97]

Following #237

• Implement stacktrie
• Use trie.Stacktrie for block and transactions hashing instead of trie.Trie currently

name                      old time/op    new time/op    delta
DeriveSha200/trie-16     221µs ± 1%     209µs ± 0%   -5.39%  (p=0.000 n=20+19)

name                      old alloc/op   new alloc/op   delta
DeriveSha200/trie-16     287kB ± 0%      60kB ± 0%  -79.02%  (p=0.000 n=20+20)

name                      old allocs/op  new allocs/op  delta
DeriveSha200/trie-16     2.89k ± 0%     1.24k ± 0%  -57.10%  (p=0.000 n=20+20)

• Optimize DeriveSha by exposing the RLP int-encoding and making use of it to write integers directly to a buffer
  Benchmark result is using trie.Trie only

name                      old time/op    new time/op    delta
DeriveSha200/std_trie-16     241µs ± 2%     220µs ± 0%  -8.76%  (p=0.000 n=19+16)

name                      old alloc/op   new alloc/op   delta
DeriveSha200/std_trie-16     271kB ± 0%     287kB ± 0%  +5.83%  (p=0.000 n=20+20)

name                      old allocs/op  new allocs/op  delta
DeriveSha200/std_trie-16     2.69k ± 0%     2.89k ± 0%  +7.40%  (p=0.000 n=19+20)

• Expose and use the encoder buffer for trie RLP actions

name                      old time/op    new time/op    delta
EncodeShortNode-16           147ns ± 9%      72ns ±10%  -51.27%  (p=0.000 n=20+20)
EncodeFullNode-16           1.56µs ±28%    0.41µs ±24%  -73.76%  (p=0.000 n=20+20)
DecodeShortNode-16           197ns ±51%     165ns ± 9%  -16.32%  (p=0.000 n=18+16)
DecodeShortNodeUnsafe-16     181ns ±45%     161ns ±20%     ~     (p=0.086 n=20+20)
DecodeFullNode-16           1.26µs ±45%    1.45µs ±33%  +14.66%  (p=0.045 n=17+20)
DecodeFullNodeUnsafe-16     1.28µs ±48%    1.23µs ±23%     ~     (p=0.473 n=20+20)

name                      old alloc/op   new alloc/op   delta
EncodeShortNode-16           48.0B ± 0%     48.0B ± 0%     ~     (all equal)
EncodeFullNode-16             864B ± 0%      576B ± 0%  -33.33%  (p=0.000 n=20+20)
DecodeShortNode-16            189B ± 0%      189B ± 0%     ~     (all equal)
DecodeShortNodeUnsafe-16      141B ± 0%      141B ± 0%     ~     (all equal)
DecodeFullNode-16           1.79kB ± 0%    1.79kB ± 0%     ~     (all equal)
DecodeFullNodeUnsafe-16     1.22kB ± 0%    1.22kB ± 0%     ~     (all equal)

name                      old allocs/op  new allocs/op  delta
EncodeShortNode-16            1.00 ± 0%      1.00 ± 0%     ~     (all equal)
EncodeFullNode-16             2.00 ± 0%      1.00 ± 0%  -50.00%  (p=0.000 n=20+20)
DecodeShortNode-16            5.00 ± 0%      5.00 ± 0%     ~     (all equal)
DecodeShortNodeUnsafe-16      4.00 ± 0%      4.00 ± 0%     ~     (all equal)
DecodeFullNode-16             34.0 ± 0%      34.0 ± 0%     ~     (all equal)
DecodeFullNodeUnsafe-16       33.0 ± 0%      33.0 ± 0%     ~     (all equal)

[rameight]

changes