feat(inputs.timex): Add plugin

[HappyTobi]

Summary

I created a new input plugin to be able to get / measure the time drifts from a Linux system to the configured ntp server.
The benefit of the plugin is, that we get the metrics from the Linux Kernel directly.
So you will get the time metrics when you are using systemd, chrony or ndpt because all the tools are calling the kernel.

As an background:
The metric can help to detect time drifts in a VM from the configure NTP server.
The metrics can also help to improve / finde issues for example with the current chrony settings because you can see the time drifts and you now have the possibility to understand them better.

Checklist

• No AI generated code was used in this PR

Related issues

[telegraf-tiger]

Thanks so much for the pull request!
🤝 ✒️ Just a reminder that the CLA has not yet been signed, and we'll need it before merging. Please sign the CLA when you get a chance, then post a comment here saying !signed-cla

[HappyTobi]

!signed-cla

[srebhan]

Thank you very much for your contribution @HappyTobi! Please find my comments in the code.

[srebhan]

Thanks @HappyTobi! Some more minor comments...

[srebhan]

Thanks @HappyTobi! Just some formatting comments and a question regarding the frequency field left...

[srebhan]

Reading more deeply into the matter, freq, ppsfreq and stabil are in 2^-16 ppm i.e. in parts-per-million. One ppm corresponds to 1e-6 or 1/10,000 %. We cannot easily compute the frequency offset in freq as we would need to know the absolute clock frequency.

Furthermore, freq is the frequency offset and not the frequency itself. So please

1. Make clear the frequency field carries an offset e.g. by naming it frequency_offset.
2. Keep the fields for the ppm information in ppm i.e. just divide them by 2^16 and adjust the field-unit suffices.

What do you think?

[srebhan]

Nice! Thanks @HappyTobi! Some last, really cosmetric, comments from my side...

[srebhan]

Awesome! Thanks a lot @HappyTobi for working with me on this PR!

[skartikey]

@HappyTobi Thanks! A couple of minor comments.

[telegraf-tiger]

Download PR build artifacts for linux_amd64.tar.gz, darwin_arm64.tar.gz, and windows_amd64.zip.
Downloads for additional architectures and packages are available below.

☺️ This pull request doesn't significantly change the Telegraf binary size (less than 1%)

📦 Click here to get additional PR build artifacts

Artifact URLs

. DEB	. RPM	. TAR . GZ	. ZIP
amd64.deb	aarch64.rpm	darwin_amd64.tar.gz	windows_amd64.zip
arm64.deb	armel.rpm	darwin_arm64.tar.gz	windows_arm64.zip
armel.deb	armv6hl.rpm	freebsd_amd64.tar.gz	windows_i386.zip
armhf.deb	i386.rpm	freebsd_armv7.tar.gz
i386.deb	ppc64le.rpm	freebsd_i386.tar.gz
mips.deb	riscv64.rpm	linux_amd64.tar.gz
mipsel.deb	s390x.rpm	linux_arm64.tar.gz
ppc64el.deb	x86_64.rpm	linux_armel.tar.gz
riscv64.deb		linux_armhf.tar.gz
s390x.deb		linux_i386.tar.gz
		linux_mips.tar.gz
		linux_mipsel.tar.gz
		linux_ppc64le.tar.gz
		linux_riscv64.tar.gz
		linux_s390x.tar.gz

[skartikey]

@HappyTobi Thanks for the contribution!