fix: remove blitzar as a dev-dependency

[tlovell-sxt]

Closes #383

Rationale for this change

Tests cannot currently be run on alternative architectures because they enable the blitzar dependency. However, this is not strictly necessary, because all tests using blitzar are behind the blitzar feature flag. So, this removes blitzar as a dev dependency, as well as making a couple related changes to the README and CI.

What changes are included in this PR?

• fix: remove blitzar as a dev-dependency
• docs: simplify README cargo test command excluding blitzar feature
• ci: check all targets in feature-specific checks of Check package job

Are these changes tested?

These changes do not change existing functionality, which is verified by existing tests.

[github-actions[bot]]

:tada: This PR is included in version 0.48.2 :tada:

The release is available on GitHub release

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