thorium: add lightweight actor count option

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
thorium_actor: include configuration

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
latency_probe: use lightweight actors

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
unitig_manager: use lightweight actor configuration

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>