Add OTel exposition format for span graph metrics

[grcevski]

From what I understood, Tempo generates traces_target_info when the OTel Collector Service Graph Connector generates target_info and we have a configuration flag to choose the one used (screenshot below).

@domasx2 do we have best practices here?

Originally posted by @cyrille-leclerc in https://github.com/grafana/beyla/pull/745#discussion_r1592180728