feat(campaign): implement MsgUpdateSpecialAllocations

[lumtis]

Implement MsgUpdateSpecialAllocations that allows updating the special allocations for a campaign

[codecov]

Codecov Report

Merging #798 (0d5a5fc) into develop (72b3631) will increase coverage by 0.02%.
The diff coverage is 13.39%.

@@             Coverage Diff             @@
##           develop     #798      +/-   ##
===========================================
+ Coverage    10.54%   10.56%   +0.02%     
===========================================
  Files          328      330       +2     
  Lines        76534    76938     +404     
===========================================
+ Hits          8073     8131      +58     
- Misses       68256    68603     +347     
+ Partials       205      204       -1     

Impacted Files	Coverage Δ
x/campaign/types/events.pb.go	0.55% <ø> (ø)
x/campaign/types/tx.pb.go	0.57% <0.57%> (+<0.01%)	⬆️
x/campaign/types/msg_update_special_allocations.go	30.76% <30.76%> (ø)
.../campaign/keeper/msg_update_special_allocations.go	100.00% <100.00%> (ø)
x/campaign/simulation/store.go	84.45% <0.00%> (+1.35%)	⬆️