This issue tracks porting the HighLevelSynthesis pass to rust as part of the #12208 epic. This pass in particular will still always require a fairly large python component, as the high level synthesis plugin interface necessitates a Python execution mode. One option is we can call Python from rust to pass a unitary array to the plugins and then operate exclusively from rust otherwise as well. The other thing worth investigating is for all the built-in synthesis methods we can have a rust only execution mode if the plugins are selected and only use python to call the external plugins if the HLSConfig contains any plugins outside the set of what's included in Qiskit.