test: add event checking to TestMigrateContract

[da1suk8]

Description

TestInstantiateContract

https://github.com/Finschia/wasmd/blob/main/docs/proto/proto-docs.md#msgmigratecontract

This PR adds an integration test for TestMigrateContract.

This test is based on https://github.com/CosmWasm/wasmd/blob/33df4aeaaa419f6aad07b94d64c0423bee0a2d21/x/wasm/keeper/msg_server_integration_test.go#L740-L825

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 #78 (9e07e41) into main (bb3a88f) will increase coverage by 0.17%.
The diff coverage is n/a.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #78      +/-   ##
==========================================
+ Coverage   62.54%   62.71%   +0.17%     
==========================================
  Files          80       80              
  Lines        9966     9966              
==========================================
+ Hits         6233     6250      +17     
+ Misses       3405     3385      -20     
- Partials      328      331       +3     

see 1 file with indirect coverage changes

[170210]

LGTM

[da1suk8]

@170210

I deleted contract_addr and I used instantiate.Address instead of contract_addr.
Thanks.