[System] Update ECS version from 8.0 to the latest

[muthu-mps]

• The current ECS version in the system integration is 8.0.0. Based on the comment here there are quite a few log.syslog.* ECS fields that are not supported in 8.0.0 for that reason these fields are declared explicitly.
• These additional syslog fields has been introduced in 8.2.0 release.

Next Steps

• Upgrade the ECS version to the latest.
• Remove the ECS field declarations for log.syslog fields and reference the fields from ECS.

[andrewkroh]

I think you mean log.syslog instead of sys.log.

[muthu-mps]

I think you mean log.syslog instead of sys.log.

Yes, Let me update the description.

[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!