feat(inputs.ntpq): Allow to specify reach output format

[srebhan]

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

resolves #2257
partially replaces #7840

This PR adds the possibility to specify the reach output format using the reach_format setting. By default the current behavior is kept, outputting the value as an octal integer just as the raw format derived from ntpq (e.g. 377). To get the decimal representation of the value use decimal (e.g. 371 ->249). More interesting is the count setting, counting the number of successful connection attempts (e.g. 371 -> 6) or the ratio setting which returns the ratio of successful attempts of the last (8) connection attempts (e.g. 371 -> 0.75).

[telegraf-tiger]

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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
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[powersj]

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