feat(agent): Add config check sub-command

[srebhan]

Summary

This PR adds a telegraf config check sub-command to check if the configuration is valid and can be successfully parsed. All plugins are initialized to validate options but are NOT started or executed. The sub-command will exit with a non-zero error code if an error occurs and with a zero error-code otherwise.

Checklist

• No AI generated code was used in this PR

Related issues

resolves #15726

[powersj]

Thanks for putting this together so quickly, I do have one comment/question

[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%)

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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

[powersj]

Thank you very much for taking a look at the flags!

[Hipska]

Just too bad there is no documentation about the cli commands anymore 😢 Now we need to download/install the binary and run the help command before we can read about this feature.

[srebhan]

@Hipska the issue with the previous documentation was that it was incorrect and a pain to maintain. If you do have a constructive proposal on how to document this with correctness and maintainability in mind, let me know!

[Hipska]

Something similar as the generation of the plugin README's? Could be just an action in the make commands and a test that informs the contributor that the repo is not in a clean state?

[srebhan]

Good call. Please open an issue and describe a bit what needs to be done... Thanks!