kmsg: Log the raw buffer if we fail to parse

[smalis-msft]

We've seen a crash here in the wild, but haven't yet figured out what exactly is failing to parse. Add some more logging so we can hopefully get this if it happens again.

[Copilot]

Pull Request Overview

This PR enhances logging for failed kmsg parses by capturing and displaying the raw buffer on errors, helping diagnose unknown parse failures.

• Extended InvalidKmsgEntry error to include the raw byte slice.
• Changed parse error handling: tests now use unwrap, the tracing task unwraps, and the diagnostic tool matches on the parse result to log failures.
• Updated test and runtime code to log or panic on invalid kmsg entries.

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
vmm_tests/vmm_tests/tests/tests/x86_64/openhcl_uefi.rs	Switched ? to unwrap on kmsg parse to panic/abort.
vmm_tests/vmm_tests/tests/tests/multiarch.rs	Switched ? to unwrap on kmsg parse to panic/abort.
support/kmsg/src/lib.rs	Changed InvalidKmsgEntry to carry the raw buffer.
petri/src/tracing.rs	Unwrapped kmsg parse in logging task, causing panic.
openhcl/ohcldiag-dev/src/main.rs	Matched parse result to print invalid entries.

Comments suppressed due to low confidence (1)

support/kmsg/src/lib.rs:73

• [nitpick] Consider adding a doc comment to InvalidKmsgEntry explaining that it carries the raw buffer for debugging, and how it will be formatted in the error message.

pub struct InvalidKmsgEntry<'a>(&'a [u8]);

[benhillis]

Backported in #1709