INIT: Flag to Add External Modules

[julienrbrt]

We should refactor this to improve the UX and have a --external-modules flag instead of a fee abstraction modules. As currently this module is mutually exclusive with the other, while it would be best if it was additive.

Originally posted by @julienrbrt in #4181 (review)

[Pantani]

I'm thinking about how to implement this issue. Should we assume all new modules are using dependency injection? We can analyse if the module has a dependency injection before adding, but if the app does not implement it, we should throw an error message, because it will be hard to know how to initiate the keeper and the module itself

[julienrbrt]

100%, when I was looking at the cosmos sdk module registry, this is a big assumptions I've made too in my spike.

We should just scaffold the app config and maybe just add a keeper.
We have no way to know if the modules has ante handler or extra init logic, so we'd need to print a warning when using this flag imho

[julienrbrt]

Using @chatton command naming suggestion: ignite s add-module [path]

We need to do some code analysis, so check the repo, read the depinject config to know what is the proto buf path to import
however we could alias the most common modules path