refactor: register x/authz module specific errors

[julienrbrt]

Description

Closes: #11577

Implement suggestion from the issue above.

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• confirmed the correct type prefix in the PR title
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[alexanderbez]

🚀 🚀 🚀

[alexanderbez]

@julienrbrt let's get the CI errors resolved (https://github.com/cosmos/cosmos-sdk/runs/6078819769?check_suite_focus=true) and we can merge this 🙌

[codecov]

Codecov Report

Merging #11670 (e39fd84) into master (75d4e41) will increase coverage by 0.06%.
The diff coverage is 57.50%.

@@            Coverage Diff             @@
##           master   #11670      +/-   ##
==========================================
+ Coverage   65.84%   65.90%   +0.06%     
==========================================
  Files         667      671       +4     
  Lines       70374    70643     +269     
==========================================
+ Hits        46336    46559     +223     
- Misses      21347    21380      +33     
- Partials     2691     2704      +13     

Impacted Files	Coverage Δ
x/authz/keeper/msg_server.go	0.00% <0.00%> (ø)
x/authz/simulation/operations.go	66.97% <0.00%> (ø)
x/authz/msgs.go	62.09% <33.33%> (ø)
x/authz/authorization_grant.go	65.71% <50.00%> (ø)
x/staking/types/authz.go	87.37% <50.00%> (ø)
x/authz/keeper/keeper.go	70.07% <63.63%> (+0.31%)	⬆️
x/group/keeper/msg_server.go	68.35% <66.66%> (ø)
x/authz/client/testutil/tx.go	98.25% <100.00%> (ø)
x/authz/keeper/grpc_query.go	63.92% <100.00%> (ø)
x/group/keeper/invariants.go	53.62% <100.00%> (ø)
... and 7 more