19292: sys/phydat: Fix unit confusion r=miri64 a=maribu
### Contribution description
Previously, `UNIT_G` was used for g-force with the correct symbol `g`, `UNIT_GR` for gram (as in kilogram) with the incorrect symbol `G` (which would be correct for Gauss), and `UNIT_GS` for Gauss with symbol `Gs` (which is an alternative correct symbol).
To avoid confusion between G-Force, Gauss, and Gram the units have been renamed to `UNIT_G_FORCE`, `UNIT_GRAM`, and `UNIT_GAUSS`. In addition, gram now uses the correct symbol `g`; which sadly is the same as for g-force. But usually there is enough context to tell them apart.
### Testing procedure
Green CI
### Issues/PRs references
None
19307: nanocoap_link_format: fix off-by-one error r=miri64 a=benpicco
Co-authored-by: Marian Buschsieweke <marian.buschsieweke@ovgu.de>
Co-authored-by: Benjamin Valentin <benpicco@beuth-hochschule.de>
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