Problem: ibc relayer don't work well with default tx prioritization strategy

[yihuang]

Solution:

• Change the default priority mechanism to be based on gas price

it'll be the default behavior in next SDK version: cosmos/cosmos-sdk#12953

• add integration test

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[codecov]

Codecov Report

Merging #848 (0a993f4) into master (e6166e1) will increase coverage by 0.08%.
The diff coverage is 66.66%.

@@            Coverage Diff             @@
##           master     #848      +/-   ##
==========================================
+ Coverage   18.93%   19.02%   +0.08%     
==========================================
  Files          93       94       +1     
  Lines       11865    11889      +24     
==========================================
+ Hits         2247     2262      +15     
- Misses       9136     9142       +6     
- Partials      482      485       +3     

Flag	Coverage Δ
integration_tests	16.71% <66.66%> (+0.09%)	⬆️
unit_tests	6.89% <0.00%> (-0.02%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
app/validator_tx_fee.go	65.21% <65.21%> (ø)
app/app.go	29.20% <100.00%> (-0.11%)	⬇️

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[tomtau]

should this one: #846 be merged first?

[yihuang]

should this one: #846 be merged first?

no, prioritization don't need any change at relayer side, we just calculate the priority based on gas price rather than fee, relayer always use a static gas price.

[tomtau]

looks all right, the integration test may need to update pystarport or what the root cause for that failed transfer is