Support RFC3339 Timestamps with Nano precision and Timezones (ie: 2023-11-28T01:55:24.811939-07:00 )

## What?
I attempted to set the field `timestamp` equal to `2023-11-28T01:55:24.811939-07:00`, but got the following error in my log line:
`Replaced invalid timestamp value in message with current time - Value <2023-11-28T01:55:24.811939-07:00> caused exception: Invalid format: "2023-11-28T01:55:24.811939-07:00" is malformed at "T01:55:24.811939-07:00".`

## Why?
Not accepting timezones isn't great.
Not accepting more precision isn't great.
Not accepting the strict rfc-3339 format isn't great.
It would be great if graylog could accept precision down to 9 decimal places, but even just 6 would be amazing. Sometimes logs are streaming very fast, and we have multiple with the same first 3 digits (which is what graylog currently accepts).

Examples are valid timestamps:
2023-11-28T01:55:24Z
2023-11-28T01:55:24-07:00
2023-11-28T01:55:24.811939Z
2023-11-28T01:55:24.811939-07:00
2023-11-28T01:55:24.811939123Z
2023-11-28T01:55:24.811939123-07:00

## Your Environment
* Graylog Version: 5.2
* Datanode Version: 5.2
* MongoDB Version: 5.0
* Operating System: Docker, on Mac
* Browser version: Chrome