Tenzir Test v2.3.1: Automatic package loading in Python tests

Python tests now automatically load their enclosing package and configured package directories, matching TQL tests. Python executors also capture package settings at construction, so explicit environment mappings select packages reliably.

🐞 Bug fixes

Automatic package loading in Python tests

Python tests now automatically load their enclosing package and additional package directories from directory-level test.yaml and the harness CLI, matching TQL tests. You no longer need to set package environment variables manually before using the Python helpers:

from tenzir_test.fixtures import Executor

executor = Executor()
executor.run("from {message: \"hello\"}")

Python tests in a package also receive TENZIR_PACKAGE_ROOT and use the nearest inputs/ directory within that package, falling back to <package>/tests/inputs. Explicit inputs overrides still take precedence.

The Executor.from_env(mapping) helper now also captures TENZIR_PACKAGE_DIRS from the supplied mapping when it is constructed, so its package selection remains stable if the environment changes later.

By @mavam in #65.