The KV ingest processor supports template snippet

[gaobinlong]

Is your feature request related to a problem? Please describe.
Unlike other ingest processors, currently the KV ingest processor doesn't support template snippet for the field and target_field parameters, we need to add this support.

Describe the solution you'd like
The KV ingest processor supports template snippet for the field and target_field parameters.

Describe alternatives you've considered
No alternatives.

[gaobinlong]

Closed by #10040.