[api] Support tx signed by ledger

[Liuhaai]

fix #2916 Extra data field EncodingType is added into the legacy tx struct, which aims to differentiate txs signed from ledgers.

[codecov[bot]]

Codecov Report

Merging #3075 (ee91de5) into master (77587d2) will increase coverage by 0.09%. The diff coverage is 74.13%.

@@            Coverage Diff             @@
##           master    #3075      +/-   ##
==========================================
+ Coverage   64.74%   64.83%   +0.09%     
==========================================
  Files         215      215              
  Lines       22094    22130      +36     
==========================================
+ Hits        14305    14349      +44     
+ Misses       6016     6001      -15     
- Partials     1773     1780       +7     

Impacted Files	Coverage Δ
api/web3server.go	54.29% <64.70%> (-0.09%)	:arrow_down:
action/rlp_tx.go	83.13% <78.04%> (+27.20%)	:arrow_up:
consensus/scheme/rolldpos/rolldposctx.go	69.43% <0.00%> (+0.47%)	:arrow_up:

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