Fork x/gov

[tbruyelle]

Copy cosmos-sdk/x/gov to x/gov to allow some customization.

Closes #5

• copy cosmos-sdk/x/gov
• change package path to github.com/atomone-hub/govgen/v1/x/gov
• remove migration and legacy stuff
• use legacy router because proposal handlers from other modules returns the legacy handlers
• fork cosmos-sdk/simapp so gov tests can compile (need to replace simapp.GovKeeper by the govgen one)
• update error code from registered errors to avoid registration panic because of duplicate
• fix duplicate proto registration (by replacing x/gov/types with legacy one in the imports)

   $ gotest ./x/gov/
   2024/02/09 15:30:06 proto: duplicate proto type registered: cosmos.gov.v1beta1.GenesisState
   panic: proto: duplicate enum registered: cosmos.gov.v1beta1.VoteOption
   
   goroutine 1 [running]:
   github.com/gogo/protobuf/proto.RegisterEnum(...)
   	/home/tom/go/pkg/mod/github.com/regen-network/[email protected]/proto/properties.go:520
   github.com/cosmos/cosmos-sdk/x/gov/types.init.3()
   	/home/tom/go/pkg/mod/github.com/cosmos/[email protected]/x/gov/types/gov.pb.go:497 +0x3d4
   FAIL	github.com/atomone-hub/govgen/v1/x/gov	0.015s
   FAIL
  

  Since both x/gov/types and cosmos-sdk/x/gov/types are imported, the proto registration happens twice for the same type name. We might want to change the type name/path, but if we do, won't we have a problem with clients using the legacy type?

[giunatale]

I've removed the need for depending on simapp in x/gov for testing. Switched over using the govgen app.

merging this code so we can go ahead with the two parallel feat planned.
We'll fix and or change this module if needed when we do the next steps