[FEATURE] Unnecessary stack trace for incomplete OSM relations

[zstadler]

Is your feature request related to a problem? Please describe.
When using Planetiler with a country/region extract, there are usually some relations that are only partially included in the extract. For example, the Geofabrik extract for Ukraine does dot fully include the way members of relation 6449148 - the "Poloniny National Park" in neighboring Slovenia.

For each such relation, Planetiler log not only states the issue with the OSM data, such as

Error processing OSM Relation 6449148 ... no rings to process after fixing

but it also adds the stack trace, as if the Planetiler itself had a fault:

Describe the solution you'd like

1. Replace the ERR severity with the de-facto INF severity.
2. Replace the elaborated message with a single line. Perhaps

   0:05:50 INF [osm_pass2:process] - Error processing OSM Relation 6449148: no rings to process after fixing