Clean up variable names

An issue to keep problematic variable names tracked.

• space_object_dt_interpolator_s -> (maybe) interpolator
• sch_dt_s_arr_pass_mask -> ?
• stt_tstmp_us
• dt_s_arr
• sch_dt_s_arr_pass, sch_dt_s_arr_pass_mask
• range_tx_m, range_rx_m