A sharded cluster application with the CRUD module and roles

[andreyaksenov]

• Created the sharded_cluster_crud application that demonstrates how to set up a sharded cluster with the crud module. It is not used anywhere in docs for now but can be used later to demonstrate the router and storage roles. Note that the example doesn't include a custom config for a role and might be extended in the future.
• Fixed a bucket_id index creation in the in the existing sharded_cluster sample (parts: id -> bucket_id): https://docs.d.tarantool.io/en/doc/sharded_cluster_crud/how-to/vshard_quick/#adding-storage-code
• Changed a router's port to 3301 in all samples and in a template - connectors use this port by default. Staging:
  • https://docs.d.tarantool.io/en/doc/sharded_cluster_crud/how-to/vshard_quick/#step-4-defining-the-cluster-topology
  • https://docs.d.tarantool.io/en/doc/sharded_cluster_crud/how-to/vshard_quick/#checking-status
  • https://docs.d.tarantool.io/en/doc/sharded_cluster_crud/release/3.0.0/#new-declarative-configuration