fix message representation for signing

[zemyblue]

Description

This PR change the msg incomming and outgoing data to contract.
It allows to input and output the actual json object to msg. This fix is based on CosmWasm/wasmd#658

Additionally, init_msg of MsgStoreCodeAndInstantiateContract is also changed to msg.

Motivation and context

The existing json.RawMessage is inconvenient because the part that needs to be used after converting json requires conversion when generating the actual tx.

How has this been tested?

Screenshots (if appropriate):

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 #513 (5b95dcc) into main (396a1fe) will increase coverage by 0.04%.
The diff coverage is 70.00%.

@@            Coverage Diff             @@
##             main     #513      +/-   ##
==========================================
+ Coverage   56.75%   56.80%   +0.04%     
==========================================
  Files         777      777              
  Lines       83389    83369      -20     
==========================================
+ Hits        47331    47355      +24     
+ Misses      33004    32959      -45     
- Partials     3054     3055       +1     

Impacted Files	Coverage Δ
x/wasm/client/cli/tx.go	14.54% <0.00%> (ø)
x/wasm/keeper/msg_server.go	0.00% <0.00%> (ø)
x/wasm/keeper/query_plugins.go	73.26% <40.00%> (-0.51%)	⬇️
x/wasm/types/tx.go	40.72% <69.23%> (+1.31%)	⬆️
x/wasm/keeper/legacy_querier.go	65.51% <80.00%> (ø)
x/wasm/keeper/querier.go	68.77% <100.00%> (+0.42%)	⬆️
x/wasm/types/proposal.go	81.14% <100.00%> (ø)
crypto/keys/internal/ecdsa/privkey.go	82.45% <0.00%> (-1.76%)	⬇️
x/consortium/keeper/querier.go
... and 9 more