timex status bitmap fields

This is sort of followup to https://github.com/prometheus/node_exporter/issues/2602

node_timex_status is a bitfield from adjtimex. Unfortunately Prometheus does not have bitmap math operations, so it's hard to check for specific bits being set in the metric.

As a start, I'd like it to be easier to detect STA_UNSYNC 0x0040 being set.

I don't know if there is prior art in node_exporter about the best way to represent bitfields.
Naively it might be exploding the single metric to unique metrics, one per flag.

Host operating system: output of uname -a

Linux (REDACTED) 5.19.0-43-generic #44~22.04.1-Ubuntu SMP PREEMPT_DYNAMIC Mon May 22 13:39:36 UTC 2 x86_64 x86_64 x86_64 GNU/Linux

What did you expect to see?

metrics for each flag

What did you see instead?

a single metric of a bitfield packed into an integer.

I would be happy to help implement this if a design is chosen.

Start by reviewing the linked issue #2602 and the current node_timex_status metric collection based on adjtimex. Compare possible representations for STA_UNSYNC and the other status flags, then identify the tests covering timex metrics. Done means a decided, documented representation exposes the requested flag metrics and the tests verify their values.