Fix weather unit tests for get_u and get_v

[SrijaVuppula]

Summary

This PR fixes the weather tests for get_u and get_v so they are actually collected and checked against the correct expected values.

Changes

• rename get_u -> test_get_u
• rename get_v -> test_get_v
• fix assertions so the returned values are compared against expected results
• correct expected component values for 45°, 135°, 225°, and 315° using sqrt(2) / 2
• rename the third parametrized expected value from u_res to v_res

Verification

Ran:

./venv/bin/pytest tests/test_weather.py -q
# Result: 12 passed

Also ran:

./.venv/bin/pytest tests/test_utils.py tests/test_weather.py -q
# Result: 39 passed

Notes

Before this change, get_u and get_v did not start with test_, so pytest would not collect them as tests.