Add relative path import support for actions directory handler

[willvedd]

🔧 Changes

As reported by #840, actions managed in directory mode produce paths that are relative to the CLI. This is in contrast to other imports, specifically the actions YAML handler, that import relative to the input file. This inconsistency can create confusion and a worse DX for developers unsure how to import code.

The solution here is to add a backup import strategy that targets the action code file relative to the input file. This will ensure backwards compatibility.

📚 References

Related issue: #840

🔬 Testing

Added new test case.

📝 Checklist

• [x] All new/changed/fixed functionality is covered by tests (or N/A)
• [x] I have added documentation for all new/changed functionality (or N/A)

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (5ab9ef5) 84.23% compared to head (47bb5d4) 84.23%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #866 +/- ## ======================================= Coverage 84.23% 84.23% ======================================= Files 115 115 Lines 3609 3610 +1 Branches 699 700 +1 ======================================= + Hits 3040 3041 +1 Misses 324 324 Partials 245 245 ```

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