Fix pack block tx order for write and readonly tx

[godeamon]

遍历交易时，判断有没有相同key的只读或者读写交易，需要保证只读交易在读写交易前打包。

[gaoweibupt]

lgtm

[codecov-commenter]

Codecov Report

Merging #304 (62636c8) into master (26f7097) will increase coverage by 0.93%. The diff coverage is 56.83%.

@@            Coverage Diff             @@
##           master     #304      +/-   ##
==========================================
+ Coverage   45.30%   46.24%   +0.93%     
==========================================
  Files         142      142              
  Lines       12488    12721     +233     
==========================================
+ Hits         5658     5883     +225     
+ Misses       5669     5660       -9     
- Partials     1161     1178      +17     

Impacted Files	Coverage Δ
bcs/ledger/xledger/tx/mempool.go	42.47% <46.51%> (+11.99%)	:arrow_up:
bcs/ledger/xledger/tx/tx.go	39.87% <50.00%> (+<0.01%)	:arrow_up:
bcs/ledger/xledger/state/state.go	46.78% <59.09%> (+0.10%)	:arrow_up:
bcs/ledger/xledger/tx/node.go	71.67% <82.55%> (+31.85%)	:arrow_up:
bcs/consensus/xpoa/xpoa.go	51.26% <0.00%> (-1.02%)	:arrow_down:
kernel/consensus/base/driver/chained-bft/smr.go	41.33% <0.00%> (+0.74%)	:arrow_up:
bcs/contract/xvm/code_manager.go	66.36% <0.00%> (+2.72%)	:arrow_up:

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