fix: tidy up x/foundation

[0Tech]

Description

This patch addresses the following items:

• Apply lint to the test files
• Fix minor document errors
• Add a test for collecting treasury
• Change error to panic where the error is not caused by user

Checklist:

• I followed the contributing guidelines and code of conduct.
• I have added a relevant changelog to CHANGELOG.md
• I have added tests to cover my changes.
• I have updated the documentation accordingly.
• I have updated API documentation client/docs/swagger-ui/swagger.yaml

[codecov]

Codecov Report

Merging #597 (512cf55) into main (728aea5) will increase coverage by 0.07%.
The diff coverage is 75.00%.

@@            Coverage Diff             @@
##             main     #597      +/-   ##
==========================================
+ Coverage   57.53%   57.61%   +0.07%     
==========================================
  Files         796      796              
  Lines       87526    87479      -47     
==========================================
+ Hits        50362    50397      +35     
+ Misses      34025    33953      -72     
+ Partials     3139     3129      -10     

Impacted Files	Coverage Δ
x/foundation/keeper/grpc_query.go	4.49% <0.00%> (+0.14%)	⬆️
x/foundation/keeper/handler.go	58.33% <0.00%> (ø)
x/foundation/keeper/msg_server.go	80.00% <10.00%> (+1.95%)	⬆️
x/foundation/keeper/grant.go	69.76% <28.57%> (+5.93%)	⬆️
x/foundation/keeper/exec.go	78.12% <66.66%> (+1.93%)	⬆️
x/foundation/keeper/vote.go	75.67% <66.66%> (+4.78%)	⬆️
x/foundation/keeper/proposal.go	72.13% <76.92%> (+2.98%)	⬆️
x/foundation/client/testutil/tx.go	99.32% <96.29%> (-0.01%)	⬇️
x/foundation/client/testutil/query.go	100.00% <100.00%> (ø)
x/foundation/client/testutil/suite.go	97.91% <100.00%> (ø)
... and 16 more

[zemyblue]

LGTM