[BUG] Protected/non-searchable metadata fields shouldn't be truncated

[frascuchon]

Describe the bug
Still for protected/non-searchable fields the metadata value limit truncation is applied. This could be skipped for this kind of field, letting users store more general info there.

Stacktrace and Code to create the bug

record.metadata["_protected"] = ... # large value here
rg.log(record,dataset)
...
ds = rg.load(dataset)
for r in ds:
   r.metadata["_protected"] # The value will be truncated

Expected behavior
The protected metadata fields should be stored as is, without data truncation.

Environment:

• Argilla Version [e.g. 1.0.0]: 1.10.0
• ElasticSearch Version [e.g. 7.10.2]: 8.5.3
• Docker Image (optional) [e.g. argilla:v1.0.0]:

Additional context
N/A