Docs: fix Doxygen warnings

[mattmundell]

What

Fix warnings from Doxygen.

Also clean up some of the doc spacing.

Why

Cleaner build. Easier to read.

[github-actions]

Dependency Review

✅ No vulnerabilities or license issues or OpenSSF Scorecard issues found.

Snapshot Warnings

⚠️: No snapshots were found for the head SHA a4bf3a5.

Ensure that dependencies are being submitted on PR branches and consider enabling retry-on-snapshot-warnings. See the documentation for more information and troubleshooting advice.

Scanned Files

None

[greenbonebot]

Scanning the following files:

base/networking.c
boreas/boreas_error.c
boreas/boreas_io.c
boreas/util.c
openvasd/openvasd.c
osp/osp.c
util/cpeutils.c
util/gpgmeutils.c
util/mqtt.c
util/passwordbasedauthentication.h
util/tlsutils.c
util/versionutils.c
util/xmlutils.c

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