fix: snmp marshal error

[MyaLongmire]

Required for all PRs:

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

resolves #10305, resolves #10304

Thank you @Doridian for the debugging and the solution!!
Store modules in an array of strings and then load them in as this ensures modules are loaded in the correct order. Also added better error messaging instead of the marshal: marshalPDU error.

[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

[Derek-K]

Just updated to 1.21.2-1, my APC UPS readings are back (except model and device name, but it could be my bad when I was trying to debug the issues earlier) Thanks!