feat(inputs.snmp): Convert octet string with invalid data to hex

[Hipska]

Summary

Some snmp data is binary encoded and displayed as HEX string with net-snmp tools (Hex-STRING: 84 C8 07 FF FD 38 54 C1). Currently Telegraf tries to interpret these bytes as string and thus resulting in non-printable characters: raw="����8T�".

This PR changes this so that they will be converted to HEX in the case of OctetString and containing not valid UTF8 characters, resulting in raw="84c807fffd3854c1". Similar fix has been done for inputs.snmp_trap: #14619.

Meanwhile I also added a new field conversion option so you can force to always convert the value to HEX string.

Checklist

• No AI generated code was used in this PR

Related issues

related to #14619
resolves #12456
resolves #3716
resolves #3478

[srebhan]

Thanks for your contribution @Hipska!

[telegraf-tiger]

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☺️ 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