Improved update of target vector configs

[aliszka]

What's being changed:

TLDR: fixes "shard is read-only" error while updating target vectors' configs.

Previously update of target vectors' configs on shard was performed for each target vector separately, starting with changing shard's state to read-only, then running update on vector index, then switching state back to ready mode.
As vector index update may be async it was undetermined when state will be set to ready again, causing update of vector index for next target vector to fail while trying to change shard's state to read-only.
Now single transition of shard's state is made. First state is changed to read-only, then updates of vector indexes of all target vectors are executed, then shard's state is changed back to ready when last (slowest) of updates finishes.

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 failed

Failed conditions
4.8% Duplication on New Code (required ≤ 3%)

See analysis details on SonarCloud