We use rustdoc style documentation for both public and private items.
By default, however, rustdoc only generates documentation for public
ones, completely ignoring anything private. As a result, a bunch of
unresolved references and other issues can make it into the
documentation of private bits.
Adjust the CI job to actually document private items and to catch these
digressions in the future. While at it, also make sure that the CI job
covers the entire workspace.

Updates the requirements on [rstest](https://github.com/la10736/rstest) to permit the latest version.
- [Release notes](https://github.com/la10736/rstest/releases)
- [Changelog](https://github.com/la10736/rstest/blob/master/CHANGELOG.md)
- [Commits](la10736/rstest@v0.25.0...v0.26.1)

---
updated-dependencies:
- dependency-name: rstest
  dependency-version: 0.26.1
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Stop specifying the patch level for any dev-dependencies. It's plain
unnecessary and causes Dependabot to increase the number of bump pull
requests.

In newer version of Rust, clippy recognizes references to Rust items
in Markdown documentation that are not surrounded by backticks. Fix one
such instance pointed out.

Bumps [actions/checkout](https://github.com/actions/checkout) from 4 to 5.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v4...v5)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '5'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

As far as I understand, this crate will typically be used when running tests, so it should be sufficient to list it as a dev-dependency.

Bumps [actions/checkout](https://github.com/actions/checkout) from 5 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v5...v6)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Behavior of the crate differs between the log and tracing backends:
while log defaults to printing messages to stderr, tracing emits them to
stdout. Until version 0.3.19 the tracing-subscriber crate did not allow
changing this default. Pull request #3187 [0] changed that and release
0.3.20 contains this logic.
Now that we can, adjust the tracing based backend to log to stderr for
consistency.

[0] tokio-rs/tracing#3187

This change bumps the version of the crate to 0.2.19. The following
notable changes have been made since 0.2.18:
- Adjusted 'tracing' output to log to stderr