Adapt conversion operators to be wary of grid mismatches

### What problem does your feature request solve?

When doing conversions we need to make sure that grid differences, e.g. mismatches due to levels or staggering are taken into account.

This is a more complex extension of #1852.

### Describe the solution you'd like

Enhance the operators in `humidity.py`, `pressure.py`, `temperature.py`, and `wind.py` to take into account the grid staggering/vertical levels if required.

### Describe alternatives you've considered

Start by reviewing the conversion operators in humidity.py, pressure.py, temperature.py, and wind.py, then compare the related work described in issue #1852. Trace how each operator handles conversions and identify where grid staggering or vertical-level differences matter. Done means the operators account for required grid mismatches during conversions.

Written by the indexing model from the issue text.