Export JoinSetTracerError from datafusion-common-runtime (apache#17877)

Fixes apache#17876

The JoinSetTracerError type is returned by set_join_set_tracer() but
was not exported in the public API, making it impossible for downstream
users to properly handle errors from this function.

This change adds JoinSetTracerError to the re-exports in lib.rs.

Author: JanKaul

datafusion/common-runtime/src/lib.rs

@@ -30,4 +30,4 @@ mod trace_utils;
 
 pub use common::SpawnedTask;
 pub use join_set::JoinSet;
-pub use trace_utils::{set_join_set_tracer, JoinSetTracer};
+pub use trace_utils::{set_join_set_tracer, JoinSetTracer, JoinSetTracerError};