application interfaces for simulation

[fedekunze]

Description

This PR introduces app interfaces in order to simplify the creation of the simulation tests (like the ones defined in /simapp/sim_test.go) for SDK based chains.

TODO:

• Remove dup code and move it to util funcs
• Open PR on Gaia Update simulation tests gaia#215

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[alexanderbez]

We should discuss this strategy and goals first. I would rather not have legitimate applications to expose their underlying baseapp and store key references. If this means apps need to duplicate a bit of code, so be it.

[fedekunze]

I would rather not have legitimate applications to expose their underlying baseapp and store key references.

👍 I will pass app.baseapp on the test and remove the GetBaseapp() function. I'll also remove the other store key getters.

[codecov]

Codecov Report

Merging #5378 into master will decrease coverage by 0.04%.
The diff coverage is 25.88%.

@@            Coverage Diff             @@
##           master    #5378      +/-   ##
==========================================
- Coverage   54.79%   54.75%   -0.05%     
==========================================
  Files         311      312       +1     
  Lines       18761    18789      +28     
==========================================
+ Hits        10280    10287       +7     
- Misses       7703     7724      +21     
  Partials      778      778

Impacted Files	Coverage Δ
simapp/state.go	0% <0%> (ø)	⬆️
simapp/test_helpers.go	0% <0%> (ø)	⬆️
simapp/app.go	89.63% <0%> (-0.43%)	⬇️
simapp/config.go	54.28% <54.28%> (ø)
simapp/utils.go	22.03% <7.14%> (-20%)	⬇️
x/mock/app.go	64.18% <0%> (+1.35%)	⬆️

[alexanderbez]

Thanks for cleaning this up @fedekunze! Left some pretty minor comments.

[alexanderbez]

ACK -- I see calls to SetupSimulation where a logger is created after. Why not use the logger from the SetupSimulation call?

[alexanderbez]

ACK