Fix gov v1beta1 support for legacy propsals (backport #1715)

[mergify]

This is an automatic backport of pull request #1715 done by Mergify.
Cherry-pick of 2a82e35 has failed:

• manual fix of test + regenerating Go files from protobuf

[codecov]

Codecov Report

Merging #1716 (c5c9252) into releases/v0.4x (56af873) will decrease coverage by 0.07%.
Report is 1 commits behind head on releases/v0.4x.
The diff coverage is 56.02%.

Additional details and impacted files

@@                Coverage Diff                 @@
##           releases/v0.4x    #1716      +/-   ##
==================================================
- Coverage           57.65%   57.59%   -0.07%     
==================================================
  Files                  62       64       +2     
  Lines                8086     8772     +686     
==================================================
+ Hits                 4662     5052     +390     
- Misses               3039     3290     +251     
- Partials              385      430      +45     

Files	Coverage Δ
x/wasm/types/codec.go	100.00% <100.00%> (ø)
x/wasm/keeper/proposal_handler_legacy.go	55.77% <55.77%> (ø)
x/wasm/types/proposal_legacy.go	53.56% <53.56%> (ø)

... and 4 files with indirect coverage changes