fix: Rename the Prometheus Input Plugin Timeout variable

[ZPascal]

Rename the Timeout Prometheus Input Plugin variable inside the configuration and the code to parse the corresponding value directly

Be aware it's a breaking change for older versions and should be merged into the next major version.

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

resolves #12565

Fix the corresponding case and renames the variable as already discussed inside #12565

[powersj]

Thanks for taking the time to quickly put a PR.

I am happy to see the new option, but instead of outright removing the old option, we want to deprecate the option. This way users get a warning before we outright remove.

[ZPascal]

@powersj You're right. That makes sense. I'll handle it later.

[powersj]

Thanks for the update and tests! Just two suggestions to make the new option show up first in the config.

[ZPascal]

@powersj Sure, it's done.

[powersj]

Thanks again!

[srebhan]

Thanks for the fix @ZPascal. I do have two small comments...

[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_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

[srebhan]

Thanks for your contribution @ZPascal!