Runtime configurable trace filters

Trace filters are currently set at startup and cannot be altered. This makes it awkward to respond to debug situations since changing log levels requires restarting the service.

Instead we should support dynamic filters, at least for the otel filter. This feature was demonstrated as part of the PoC #2033.

I think a dedicated admin port/server would be ideal for this, and does not need to be protobuf unless that is easier. A basic REST endpoint taking in the filter string is sufficient.

Some additional considerations:

- Should the config survive service resets? If so, how does that interact with the setting via CLI on startup?
- Should the endpoint return the current setting for `GET`?