Support raft rf scale (part 2)

[aliszka]

What's being changed:

• changes approach to shard reinit: removes dedicated method, uses Shard::Shutdown() followed by NewShard() calls.
• updates replication factor on Index::Config when scaling out to fix Index::replicationEnabled() calls after scaling.

Review checklist

• Documentation has been updated, if necessary. Link to changed documentation:
• Chaos pipeline run or not necessary. Link to pipeline:
• All new code is covered by tests where it is reasonable.
• Performance tests have been run or not necessary.

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
1.8% Duplication on New Code

See analysis details on SonarCloud