[Data view field] Restore/improve validation message when navigating between documents via preview panel

[jughosta]

Kibana version: main

Description of the problem including expected versus actual behavior: If not all documents have values for the field which is used in the script, then validation error can disappear or become confusing when navigating between documents for preview. I would expect it get back to the original validation message which was helpful.

Steps to reproduce:

1. Open "Create field" flyout
2. Enter a script which uses a field with a missing value for the current document in preview
3. Navigate to next document in preview (with or without a value for the field) and return to the initial document
4. Observe that validation message becomes generic or missing.

POST test_this/_doc
{
  "message": "hi there"
}
POST test_this/_doc
{
  "another_message": "hallöchen"
}

Related: https://discuss.elastic.co/t/runtime-fields-cant-be-saved-because-highlighted-errors-need-to-be-fixed-but-none-are-highlighted/359121

[elasticmachine]

Pinging @elastic/kibana-data-discovery (Team:DataDiscovery)