Parse `--home` flag earlier

[julienrbrt]

Having a custom node location (using the --home flag) is causing many issues at node instantiation.
We have been using many hacks to avoid using the default one:

Default one set here:

• cosmos-sdk/simapp/app.go

  Lines 186 to 191 in 340f85f

  	userHomeDir, err := os.UserHomeDir()
  	if err != nil {
  	panic(err)
  	}
  	DefaultNodeHome = filepath.Join(userHomeDir, ".simapp")

  
  Hack 1:

• cosmos-sdk/simapp/simd/cmd/root_di.go

  Line 43 in 340f85f

  simtestutil.NewAppOptionsWithFlagHome(tempDir()),

  cosmos-sdk/simapp/simd/cmd/root.go

  Line 33 in 340f85f

  tempApp := simapp.NewSimApp(log.NewNopLogger(), dbm.NewMemDB(), nil, true, simtestutil.NewAppOptionsWithFlagHome(tempDir()))

  
  Hack 2:
  

  cosmos-sdk/simapp/simd/cmd/root.go

  Lines 117 to 120 in 340f85f

  	initClientCtx, err = config.ReadDefaultValuesFromDefaultClientConfig(initClientCtx, customClientTemplate, customClientConfig)
  	if err != nil {
  	panic(err)
  	}

The issue is the --home flag is parsed too late (at cobra run (RunE and & co), while most of the instantiation is done before the commands and the flag parsing.

We need to parse the --home flag earlier or rely solely on environment variable. Best would be at init() or somewhere in main() before any other logic, and pass it down.