Adding label field

[srclosson]

Why?

Datalinks need the option of being labeled uniquely from other labels. Some panels may parse out logging messages themselves, but to decorate a parsed logging message, it needs to be labeled and decorated in the dataframe.

BUT, one may not want duplicate labels in the dataframe. So, allow a custom label.

Example:

<date> INFO - hostIP=192.168.1.1

Will get parsed by the log panel and show 192.168.1.1, with a label of hostIP

With the configuration:
field: raw
label: host_ip_address
regex: hostIP=([0-9\.]+)

You will get the label host_ip_address instead of hostIP, which will also appear in the log panel in the explore view (but wont be able to have datalinks because it was not in the dataframe, but host_ip_address will.

Hopefully this makes sense.

[vickyyyyyyy]

LGTM! 🔥

Also, it doesn't look like we have a story for this component, can it be added? (Doesn't need to be done within this same PR)