feat: add exclude_root_certs option to x509_cert plugin

[jjh74]

Required for all PRs:

• Updated associated README.md.
• Wrote appropriate unit tests.
• Pull request title or commits are in conventional commit format (e.g. feat: or fix:)

resolves #9427

This PR adds exclude_root_certs configuration option(defaults to false) to x509_cert plugin. When exclude_root_certs is true then x509_cert doesn't add metrics for root (and intermediate) certs.

[[inputs.x509_cert]]
  sources = [ "https://www.influxdata.com:443" ]
  exclude_root_certs = false

outputs:

> x509_cert,common_name=sni.cloudflaressl.com,country=US,host=hidden,issuer_common_name=Cloudflare\ Inc\ ECC\ CA-3,locality=San\ Francisco,organization=Cloudflare\,\ Inc.,province=California,public_key_algorithm=ECDSA,san=www.influxdata.com\,sni.cloudflaressl.com,serial_number=f0e13e9cfe14710ee2e23d4f7255351,signature_algorithm=ECDSA-SHA256,source=https://www.influxdata.com:443,verification=valid age=13523310i,enddate=1650671999i,expiry=18012688i,startdate=1619136000i,verification_code=0i 1632659310000000000
> x509_cert,common_name=Cloudflare\ Inc\ ECC\ CA-3,country=US,host=hidden,issuer_common_name=Baltimore\ CyberTrust\ Root,organization=Cloudflare\,\ Inc.,public_key_algorithm=ECDSA,serial_number=a3787645e5fb48c224efd1bed140c3c,signature_algorithm=SHA256-RSA,source=https://www.influxdata.com:443,verification=valid age=52530022i,enddate=1735689599i,expiry=103030288i,startdate=1580129288i,verification_code=0i 1632659310000000000

and with exclude_root_certs = true:

> x509_cert,common_name=sni.cloudflaressl.com,country=US,host=hidden,issuer_common_name=Cloudflare\ Inc\ ECC\ CA-3,locality=San\ Francisco,organization=Cloudflare\,\ Inc.,province=California,public_key_algorithm=ECDSA,san=www.influxdata.com\,sni.cloudflaressl.com,serial_number=f0e13e9cfe14710ee2e23d4f7255351,signature_algorithm=ECDSA-SHA256,source=https://www.influxdata.com:443,verification=valid age=13523402i,enddate=1650671999i,expiry=18012596i,startdate=1619136000i,verification_code=0i 1632659402000000000

[jjh74]

Hi,
@srebhan do you have time to take a look if this PR is ok ?

[srebhan]

@jjh74 I'm not an expert in x509 and cannot judge if your approach is sound. I only checked the code style/structure...
I have one comment regarding your test. Furthermore, please resolve the merge conflict.

@sspaink or @powersj can you maybe take a look at this PR?

[srebhan]

Looks good to me. Thanks for contributing this PR @jjh74!

[telegraf-tiger]

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

📦 Looks like new artifacts were built from this PR.

Expand this list to get them here ! 🐯

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	s390x.rpm	linux_amd64.tar.gz
mipsel.deb	x86_64.rpm	linux_arm64.tar.gz
ppc64el.deb		linux_armel.tar.gz
s390x.deb		linux_armhf.tar.gz
		linux_i386.tar.gz
		linux_mips.tar.gz
		linux_mipsel.tar.gz
		linux_ppc64le.tar.gz
		linux_s390x.tar.gz
		static_linux_amd64.tar.gz