fix(parsers.xpath): Allow resolving extensions

[srebhan]

Summary

Currently, the XPath parser fails to resolve fields containing extensions due to the fact that extensions are currently not registered globally and thus cannot be resolved by the unmarshaller.

Instead of registering extensions globally this PR uses a parser-specific registry to avoid side effects between different parsers. Unfortunately, extensions are usually distributed across different files that are not imported by the main file. Therefore, all extensions need to be loaded explicitly additionally to the main file. As a consequence the xpath_protobuf_file option needs to be replaced by xpath_protobuf_files (plural) to be able to specify multiple input files.

Checklist

• No AI generated code was used in this PR

Related issues

resolves #15571

[telegraf-tiger]

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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

[mstrandboge]

Looks great!

[powersj]

Thanks!