Unify timestamp field names

[Rohlik]

Hello Grafana guys 👋🏼,
We used the Grafana helm chart and noticed that timestamp representation differs between the grafana-sc-dashboard and the grafana containers. When you have json logging enabled then your logs probably look like this:

# grafana-sc-dashboard
{"time": "2024-04-24T09:09:26.606514+00:00", "taskName": null, "msg": "Found a folder override annotation, placing the metrics-dashboard-15.1.0-dev1 in: /tmp/dashboards/dev1", "level": "INFO"}
# grafana
{"level":"info","logger":"settings","msg":"Config overridden from Environment variable","t":"2024-04-23T06:59:14.858660879Z","var":"GF_PATHS_LOGS=/var/log/grafana"}

You have a t field in one container and for the next one, time. Log parsing is unnecessarily complicated for some log collectors like FluentD when you count with time (default key name for the time field), but you have t 😞.

Can you please consider to rename that field t to time 🙏🏼?