Deprecate EsFetcher elasticsearch.fetchDocFromEs=true

The elasticsearch.fetchDocFromEs=true enables to fetch document from elastic using the _source in order to build a partial document model with it, the goal is to avoid to read document from the backend.

This experimental feature was never shown to be effective or improve scaling during benchmark campaign, because:

• it is more stress on elastic and it impacts search and indexing activity, mainly because the source content needs to be read (disk IO) and transmitted (network IO).

• accessing a missing field (not part of the configuration) or any internal fields of the doc is going to load the doc from the backend anyway, but in an inefficient way (one doc at a time vs a list of docs in the first place)

When using VCS it might be faster on limited cases, because reading doc from backend requires lots of roundtrip (one per schema) but this is not true for mongodb where reading docs has never been a problem.

For the above reasons we want to mark this feature (EsFetcher) as deprecated on 2023.