3.0 use manual cluster bootstrap (#3981)

Author: andreyaksenov

doc/code_snippets/snippets/sharding/instances.enabled/sharded_cluster/README.md

@@ -9,7 +9,7 @@ To run the cluster, go to the `sharding` directory in the terminal and perform t
 1. Install dependencies defined in the `*.rockspec` file:
 
    ```console
-   $ tt build
+   $ tt build sharded_cluster
    ```
 
 2. Run the cluster:
@@ -23,16 +23,25 @@ To run the cluster, go to the `sharding` directory in the terminal and perform t
    ```console
    $ tt connect sharded_cluster:router-a-001
    ```
+   
+4. Perform the initial cluster bootstrap:
+
+   ```console
+   sharded_cluster:router-a-001> require('vshard').router.bootstrap()
+   ---
+   - true
+   ...
+   ```
 
-4. Insert test data:
+5. Insert test data:
 
    ```console
    sharded_cluster:router-a-001> insert_data()
    ---
    ...
    ```
 
-5. Connect to storages in different replica sets to see how data is distributed across nodes:
+6. Connect to storages in different replica sets to see how data is distributed across nodes:
 
    a. `storage-a-001`:
 

doc/code_snippets/snippets/sharding/instances.enabled/sharded_cluster/router.lua

@@ -1,7 +1,5 @@
 local vshard = require('vshard')
 
-vshard.router.bootstrap()
-
 function put(id, band_name, year)
     local bucket_id = vshard.router.bucket_id_mpcrc32({ id })
     vshard.router.callrw(bucket_id, 'put', { id, bucket_id, band_name, year })