feat: Add license checking tool

[srebhan]

• Updated associated README.md.
• Wrote appropriate unit tests.
• Pull request title or commits are in conventional commit format

This PR adds a small tool to verify the license information in docs/LICENSE_OF_DEPENDENCIES.md against the repository content of the individual dependencies.

To run the tool first build it with make build_tools and then

./tools/license_checker/license_checker -whitelist ./tools/license_checker/data/whitelist -cache .licenses.cache .

This will use the whitelisting for github.com/eclipse/paho.mqtt.golang and caches the classification results.

[powersj]

Briefly looked through this, this needs a README on how to run it and details on the whitelist documented.

Other than the items in the whitelist, have you run into many mistakes or issues with trying to parse the licenses? I see the threshold setting and was wondering if you had to play with it to get this to work consistently?

[srebhan]

@MyaLongmire and @sspaink removed the cache as discussed and added to nightly build. Please have a look and let me know what you think!

[telegraf-tiger]

Download PR build artifacts for linux_amd64.tar.gz, darwin_amd64.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_i386.zip
armel.deb	armv6hl.rpm	freebsd_amd64.tar.gz
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
		static_linux_amd64.tar.gz

[sspaink]

Thank you for making this!

[powersj]

Awesome! Thank you!