Provide information about the specific functionality used when creating a specific index

[martijnvg]

Since an index using LogsDB may or may not have Synthetic source enabled, and this can vary amongst backing indices within the same data stream, it would be nice to be able to quickly and easily see the mode of features like Synthetic source (and things like CLP in the future) for a given index. This could make it easier for Kibana to display this information. It is also likely helpful in support scenarios, in case a customer reports an issue with a LogsDB index, one of our first questions is likely going to be "is it using synthetic source or not" so there should be an easy way to gather this information.

[elasticsearchmachine]

Pinging @elastic/es-storage-engine (Team:StorageEngine)