feat(inputs.lustre2): Add eviction_count field

[lukeyeager]

Adds support for https://review.whamcloud.com/c/fs/lustre-release/+/40528.

I'll rebase after #15042 is merged.

NOTE: according to https://wiki.lustre.org/Lustre_Monitoring_and_Statistics_Guide#Reading_/proc_vs_lctl it is technically safer to use lctl get_param *.*.eviction_count than parsing files in sysfs/procfs. In this MR I am simply following the existing convention for the plugin. Perhaps in the future we should switch to using lctl get_param for maximum portability. Tests would require mocking the exec.Command output, as is done for other plugins.

[powersj]

Thanks!

[powersj]

Ah I missed the lint issues:

plugins/inputs/lustre2/lustre2.go:604:65       revive    empty-lines: extra empty line at the end of a block
plugins/inputs/lustre2/lustre2.go:687:3        revive    early-return: if c { ... } else { ... return } can be simplified to if !c { ... return } ...
plugins/inputs/lustre2/lustre2_test.go:593:31  gocritic  filepathJoin: "sys/fs/lustre" contains a path separator

[telegraf-tiger]

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amd64.deb	aarch64.rpm	darwin_amd64.tar.gz	windows_amd64.zip
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armel.deb	armv6hl.rpm	freebsd_amd64.tar.gz	windows_i386.zip
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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
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		linux_ppc64le.tar.gz
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