feat(inputs.gnmi): Add yang-model decoding of JSON IETF payloads

[srebhan]

Summary

This PR adds decoding of JSON IETF payloads according to the YANG model for non-standard base-types.

Checklist

• No AI generated code was used in this PR

Related issues

resolves #15046

[powersj]

Thanks for this! I feel more confident about it given the actual testing done by the user.

[srebhan]

@powersj I simplified the leaf lookup a bit more and off-loaded namespace-module mapping to the init-phase...

[telegraf-tiger]

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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