`.tsp._history`: drop `feed_is_live` syncing, another seg flag

The `await feed_is_live.wait()` is more or less pointless and would only
cause slower startup afaig (as-far-as-i-grok) so i'm masking it here.
This also removes the final `strict_exception_groups=False` use from the
non-tests code base, flipping to the `tractor.trionics` collapser once
and for all!

piker/tsp/_history.py

@@ -1046,12 +1046,15 @@ async def tsdb_backfill(
                     last_tsdb_dt,
                 ) = tsdb_entry
 
+            # await tractor.pause()
+
             # if there is a gap to backfill from the first
             # history frame until the last datum loaded from the tsdb
             # continue that now in the background
-            async with trio.open_nursery(
-                strict_exception_groups=False,
-            ) as tn:
+            async with (
+                tractor.trionics.collapse_eg(),
+                trio.open_nursery() as tn,
+            ):
 
                 bf_done = await tn.start(
                     partial(
@@ -1322,8 +1325,14 @@ async def manage_history(
     # TODO: maybe it should be a subpkg of `.data`?
     from piker import storage
 
+    storemod: ModuleType
+    client: StorageClient
+    tn: trio.Nursery
     async with (
-        storage.open_storage_client() as (storemod, client),
+        storage.open_storage_client() as (
+            storemod,
+            client,
+        ),
 
         # NOTE: this nursery spawns a task per "timeframe" (aka
         # sampling period) data set since normally differently
@@ -1392,7 +1401,7 @@ async def manage_history(
             some_data_ready.set()
 
             # wait for a live feed before starting the sampler.
-            await feed_is_live.wait()
+            # await feed_is_live.wait()
 
             # yield back after client connect with filled shm
             task_status.started((