Official service-mngr to `tractor.hilevel` move

Such that we maintain that subsys in the actor-runtime repo (with
hopefully an extensive test suite XD).

Port deats,
- rewrite `open_service_mngr()` as a thin wrapper that delegates into
  the new `tractor.hilevel.open_service_mngr()` but with maintenance of
  the `Services` class-singleton for now.
- port `.service._daemon` usage to the new
  `ServiceMngr.start_service_ctx()` a rename from
  `.start_service_task()` which is now likely destined for the soon
  supported `tractor.trionics.TaskMngr` nursery extension.
- ref the new `ServiceMngr.an: ActorNursery` instance var name.

Other,
- always enable the `tractor.pause_from_sync()` support via `greenback`
  whenever `debug_mode` is set at `pikerd` init.

piker/brokers/binance/api.py

@@ -567,7 +567,6 @@ class Client:
     ) -> str:
         return {
             'USDTM': 'usdtm_futes',
-            'SPOT': 'spot',
             # 'COINM': 'coin_futes',
             # ^-TODO-^ bc someone might want it..?
         }[pair.venue]

piker/tsp/__init__.py

@@ -458,15 +458,13 @@ async def start_backfill(
                     'bf_until <- last_start_dt:\n'
                     f'{backfill_until_dt} <- {last_start_dt}\n'
                 )
-                # UGH: what's a better way?
+
-                # TODO: backends are responsible for being correct on
+                # ugh, what's a better way?
-                # this right!?
+                # TODO: fwiw, we probably want a way to signal a throttle
-                # -[ ] in the `ib` case we could maybe offer some way
+                # condition (eg. with ib) so that we can halt the
-                #     to halt the request loop until the condition is
+                # request loop until the condition is resolved?
-                #     resolved or should the backend be entirely in
+                if timeframe > 1:
-                #     charge of solving such faults? yes, right?
+                    await tractor.pause()
-                # if timeframe > 1:
-                #     await tractor.pause()
                 return
 
             assert (
@@ -580,7 +578,6 @@ async def start_backfill(
                     'crypto',
                     'crypto_currency',
                     'fiat',  # a "forex pair"
-                    'perpetual_future',  # stupid "perps" from cex land
                 }:
                     # for now, our table key schema is not including
                     # the dst[/src] source asset token.