Crisis Module Manager Fixes

[alexanderbez]

• Call the crisis module's end blocker in SimApp
• Fix invariant registration bug by passing the crisis module by reference
• Cleanup godocs and misc

closes: #4803

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• Wrote tests

• Updated relevant documentation (docs/)

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[fedekunze]

LGTM

[alexanderbez]

with regards to test_sim_import_export failing, the only difference this PR introduces is that we now actually run invariants during InitGenesis (before we weren't). So sim runs, state is exported, state is than imported, finally InitGenesis gets called and all the invariants execute upon which the same one always fails (from x/distributions InitGenesis):

panic: calculated final stake for delegator cosmos12h8cwerpnvwjfsgw5cehrpdghtg2at7ctkac50 greater than current stake
	final stake:	35411088.000000000000000000
	current stake:	34565140.560069448745397772

Interesting enough, regardless of the sim seed, final stake is always truncated to zero.

/cc @rigelrozanski

[rigelrozanski]

ACK - great work on finding the solution @alexanderbez !

[codecov]

Codecov Report

Merging #4854 into master will increase coverage by 0.04%.
The diff coverage is 57.89%.

@@            Coverage Diff            @@
##           master   #4854      +/-   ##
=========================================
+ Coverage   54.25%   54.3%   +0.04%     
=========================================
  Files         269     271       +2     
  Lines       17302   17344      +42     
=========================================
+ Hits         9388    9418      +30     
- Misses       7216    7228      +12     
  Partials      698     698