decrease `cargo test` time for git workflows

[jtmoon79]

Problem

The time to complete cargo test is about 15 minutes long. It is run an additional time for grcov coverage report. That's at least 30 minutes per git push and git tag.

This is a long wait for every push and tag.

Solution

Decrease the time required somehow.

[jtmoon79]

Current runtime from Run 4827538011

• Longest job from first stages: 12:14 build MSRV 1.67.1 on macos-latest
• Longest job from second stages: 7:57 test
• Longest job from third stages: 3:20 run s4
• Longest job from fourth stages: 27:22 grcov

[jtmoon79]

Relates to #218