In at least one instance (4615603), log index keys as strings instead of deflated JSON

Downstream consumers of structured logs could have problems persisting/rendering log line 4615603, and potentially others.

The convention of logging index keys as Extended JSON with deflated key names (e.g., { "": "valueA", "": "valueB" } in index {a:1, b:1}) will probably lead many consumers to receive a single-field document with only the last value (e.g., { "": "valueB" }) unless they introduce special handling.

To be clear, we do log the index key correctly. It is just in a convention that many clients will readily mangle.

At a minimum, can log line 4615603 log attr.indexKeyData.key as a string instead of Extended JSON? There may be a more generic solution that fixes all log lines impacted, but it is yet unclear how many log lines are impacted.