Improve variable name logging in error reporting

[aoyako]

Pyarts version: '2.6.14'

Functions that use chk_rte_pos/los validate both rte_pos/los and rtp_pos/los. However, when an error occurs in functions that take rtp_pos/los, the error message incorrectly refers to rte_pos/los, which is confusing. It can be observed by several functions, such as InterpGriddedField2ToPosition and InterpSurfaceFieldToPosition.