Generate templates where @timestamp uses date_nanos if timestamp.precision is set to nanosecond.

[cmacknz]

We now support nanosecond precision timestamps in events: #31553

We could further enhance our support for nanosecond precision timestamps by generating mapping templates that specify that the timestamp field should be date_nanos.

There are some issues in Kibana that would need to be resolved before we could support this:

• [Logs UI] The UI throws error when @timestamp format is date_nanos kibana#88290
• 64 bit number/integer support in Kibana kibana#40183

The request for this enhancement can be found in the original nanosecond timestamp issue comments: #15871 (comment)

[elasticmachine]

Pinging @elastic/elastic-agent-data-plane (Team:Elastic-Agent-Data-Plane)

[botelastic]

Hi!
We just realized that we haven't looked into this issue in a while. We're sorry!

We're labeling this issue as Stale to make it hit our filters and make sure we get back to it as soon as possible. In the meantime, it'd be extremely helpful if you could take a look at it as well and confirm its relevance. A simple comment with a nice emoji will be enough :+1.
Thank you for your contribution!