feat(agent): output buffer persistence

[mstrandboge]

Summary

Implements the write-through buffer persistence strategy detailed in the spec added in #14928.

Currently this PR is mostly a draft of separating the output buffer into multiple implementations, as well as experimentation with a WAL file library. Largest outstanding issue is around metric serialization to []byte.

• Using the influx parser+serializer causes a cyclical import, but also drops the metric value type field. However this is probably the cleanest option to investigate since it would make the WAL files easy to re-import
• Another suggestion was to use encoding/gob, which is what the PR is currently doing. However this has issues with un-exported fields, so I need to look more into how to work around this

Checklist

• [X] No AI generated code was used in this PR

Related issues

Related to #802, #14805

[powersj]

@DStrand1,

Thanks for the PR, super excided to see this. To capture what we talked about in pairs; specifically, to have you address some of the initial comments and switch to the proposed WAL library.

Let's plan to talk through where you are at or any issues with the new library in Monday's pairs.

Thanks!

[mstrandboge]

Remaining comments are related to using the WAL file Batch function, I will work on switching to that next

[telegraf-tiger[bot]]

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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]

Superseded by #15564