thorium: perform message demultiplexing in workers

Link: https://github.com/GeneAssembly/biosal/issues/751
Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
thorium: use a round-robin approach for demultiplexing in worker

Link: https://github.com/GeneAssembly/biosal/issues/751
Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
thorium: improve LTTng tracepoints in worker

Link: https://github.com/GeneAssembly/biosal/issues/751
Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>