Investigate ease of plugins having own logging channel/level

A plugin might want to control its own logging level (i.e. DEBUG or even TRACE instead of INFO, but only for it).

Investigate if we've made this easy, and if not, adjustments to make it so.

There's also the possibility that a plugin would want its own logging file, and we should make that easy as well.

Start by tracing how plugin logging is currently configured and whether a plugin can select its own logging level or output file. Compare the existing behavior with the requested DEBUG/TRACE levels and per-plugin files. Done means the investigation identifies the required adjustments and makes plugin-specific logging straightforward.

Written by the indexing model from the issue text.