Wizard: Prevent entry of the several bootstrap servers into a single field

[BulatKha]

Describe the bug (Actual behavior)

It is possible to type into a single "Bootstrap servers" field a list of several as comma-separated values. E.g.:
'kafka0:29092,kafka1:29092, .. kafkaN' in bootstrap server address and port in the next.
After clicking on 'Submit', they are created as separate nodes.

Expected behavior

Some field validation should prevent saving field values as such.

Set up

450ec66
the 'wizard' branch

Steps to Reproduce

1. Set up the Kafka UI with a setting
   DYNAMIC_CONFIG_ENABLED: true
2. Open dashboard and click 'Configure' for and existing cluster or 'Configure new cluster'.
3. Enter several comma-separated bootstrap servers with ports into a single 'Bootstrap servers' field like this:
   
4. Click Submit button and check the cluster config:
   

Additional context