feat(campaign): implement query special-allocations-balance

[lumtis]

special-allocations-balance get the final token balance for special allocation.

This query is to be used by the client to verify the genesis is correctly formatted:

bank:
 supply == genesisDistribution
claim:
 airdropSupply == claimableAirdrop

[codecov]

Codecov Report

Merging #802 (6fb0761) into develop (11fb463) will decrease coverage by 0.03%.
The diff coverage is 5.74%.

@@             Coverage Diff             @@
##           develop     #802      +/-   ##
===========================================
- Coverage    10.56%   10.53%   -0.04%     
===========================================
  Files          330      332       +2     
  Lines        76938    77421     +483     
===========================================
+ Hits          8129     8155      +26     
- Misses       68604    69059     +455     
- Partials       205      207       +2     

Impacted Files	Coverage Δ
...gn/client/cli/query_special_allocations_balance.go	0.00% <0.00%> (ø)
x/campaign/types/query.pb.gw.go	0.00% <0.00%> (ø)
x/campaign/types/query.pb.go	0.63% <0.54%> (-0.01%)	⬇️
...ampaign/keeper/grpc_special_allocations_balance.go	90.00% <90.00%> (ø)
x/campaign/simulation/store.go	81.08% <0.00%> (-2.03%)	⬇️

[aljo242]

We should have test cases for the two times that CoinsFromTotalSupply() can throw an error in this function.