New Remap function for to_syslog_facility

[jbradleynh]

Similar to request to map syslog severity levels to human readable keywords from #5500 it would be helpful to have a means to remap syslog facility codes to their keyword as well.

Use-cases

When parsing events message from the journald source, the raw facility values could be enriched with a simple remap transform to down stream labeling

Proposal

create a remap-function to_syslog_facility which could produce the facility name:

to_syslog_facility(10)
=> "authpriv"

References

• Cleanup journald source context fields #4304 related to need for cleanup of journald sources

[JeanMertz]

Resolved in #5770