Vue-storefront: Move entity types registration and gql queries on the module level

[yuriboyko]

What is the motivation for adding / enhancing this feature?

Currently all queries are located on the searchAdapter side each of them is related to the certain module work . So it probably make sense to move queries for search adapter on the module level

so each module should have search adapters folders structure
something like this:
'search-adapter'
-> 'graphql'
-> 'api'

where should be a registeration of all required for this module search adapter entity types

[lukeromanowicz]

Related to #2225

[mirkocesaro]

Hi @filrak, I and @nuovecode would like to take this issue for the hackathon5. Could you please assign to us?

[pkarw]

Done!