refactor(tests): use relative imports in ./tests (ethereum#1848)

Co-authored-by: danceratopz <[email protected]>

Author: kclowes

CHANGELOG.md

@@ -57,6 +57,7 @@ Users can select any of the artifacts depending on their testing needs for their
 
 ### 📋 Misc
 
+- 🔀 Use only relative imports in `tests/` directory ([#1848](https://github.com/ethereum/execution-spec-tests/pull/1848)).
 - 🔀 Misc. doc updates, including a navigation footer ([#1846](https://github.com/ethereum/execution-spec-tests/pull/1846)).
 - 🔀 Remove Python 3.10 support ([#1808](https://github.com/ethereum/execution-spec-tests/pull/1808)).
 - 🔀 Modernize codebase with Python 3.11 language features ([#1812](https://github.com/ethereum/execution-spec-tests/pull/1812)).