Scaffold simulation testing with `simapp`

[lumtis]

Is your feature request related to a problem? Please describe.
Scaffold simulation testing using simapp of Cosmos SDK as part of our test templates https://docs.cosmos.network/master/building-modules/simulator.html

Describe the solution you'd like

When an app is scaffolded starport s chain:

• Update app.go template to instantiate simulation manager
• Scaffold a general simulation test in app package that includes a benchmark test

When a module is scaffolded starport s module

• Scaffold implementation of AppModuleSimulation
• Could be interesting to implement Scaffold parameters for a module #1699 first in order to have a customized RandomizedParams method

When a message is scaffolded starport s message

• Scaffold an empty operation method to simulate the message with a default weight and that returns simtypes.NoOpMsg