Port `.data._web_bs` stuff to strict-EGs

Using `tractor.trionics.collapse_eg()` as needed and doing
some renames, in similar style as elsewhere:
- `pcs` -> `rent_cs`,
- `n` -> `tn` for nursery handles,

Also,
- tweak the `._reconnect_forever()` while loop to use the
  (also) `trio`-internal
  `mc_state: trio._channel.MemoryChannelState = snd._state` instead
  of `snd._close` to poll for open send/receive consumer task counts
  since,
    1. it seems more reliable then using the `snd._closed`,
    2. there's no other way to access the info.. afaik?

- handle `ConnectionRejected` explicitly alongside handshake-errs as
  a retry case.
- add a base-exc handler which `.exception()` reports the reconnect
  attempt failure explicitly.
- drop some lingering `Optional` usage.

piker/data/_web_bs.py

@@ -27,7 +27,6 @@ from functools import partial
 from types import ModuleType
 from typing import (
     Any,
-    Optional,
     Callable,
     AsyncContextManager,
     AsyncGenerator,
@@ -35,6 +34,7 @@ from typing import (
 )
 import json
 
+import tractor
 import trio
 from trio_typing import TaskStatus
 from trio_websocket import (
@@ -167,7 +167,7 @@ async def _reconnect_forever(
 
     async def proxy_msgs(
         ws: WebSocketConnection,
-        pcs: trio.CancelScope,  # parent cancel scope
+        rent_cs: trio.CancelScope,  # parent cancel scope
     ):
         '''
         Receive (under `timeout` deadline) all msgs from from underlying
@@ -192,7 +192,7 @@ async def _reconnect_forever(
                         f'{url} connection bail with:'
                     )
                     await trio.sleep(0.5)
-                    pcs.cancel()
+                    rent_cs.cancel()
 
                     # go back to reonnect loop in parent task
                     return
@@ -204,7 +204,7 @@ async def _reconnect_forever(
                         f'{src_mod}\n'
                         'WS feed seems down and slow af.. reconnecting\n'
                     )
-                    pcs.cancel()
+                    rent_cs.cancel()
 
                     # go back to reonnect loop in parent task
                     return
@@ -228,7 +228,12 @@ async def _reconnect_forever(
     nobsws._connected = trio.Event()
     task_status.started()
 
-    while not snd._closed:
+    mc_state: trio._channel.MemoryChannelState = snd._state
+    while (
+        mc_state.open_receive_channels > 0
+        and
+        mc_state.open_send_channels > 0
+    ):
         log.info(
             f'{src_mod}\n'
             f'{url} trying (RE)CONNECT'
@@ -237,10 +242,11 @@ async def _reconnect_forever(
         ws: WebSocketConnection
         try:
             async with (
-                trio.open_nursery() as n,
                 open_websocket_url(url) as ws,
+                tractor.trionics.collapse_eg(),
+                trio.open_nursery() as tn,
             ):
-                cs = nobsws._cs = n.cancel_scope
+                cs = nobsws._cs = tn.cancel_scope
                 nobsws._ws = ws
                 log.info(
                     f'{src_mod}\n'
@@ -248,7 +254,7 @@ async def _reconnect_forever(
                 )
 
                 # begin relay loop to forward msgs
-                n.start_soon(
+                tn.start_soon(
                     proxy_msgs,
                     ws,
                     cs,
@@ -262,7 +268,7 @@ async def _reconnect_forever(
 
                     # TODO: should we return an explicit sub-cs
                     # from this fixture task?
-                    await n.start(
+                    await tn.start(
                         open_fixture,
                         fixture,
                         nobsws,
@@ -272,11 +278,23 @@ async def _reconnect_forever(
                 # to let tasks run **inside** the ws open block above.
                 nobsws._connected.set()
                 await trio.sleep_forever()
-        except HandshakeError:
+
+        except (
+            HandshakeError,
+            ConnectionRejected,
+        ):
             log.exception('Retrying connection')
+            await trio.sleep(0.5)  # throttle
 
-        # ws & nursery block ends
+        except BaseException as _berr:
+            berr = _berr
+            log.exception(
+                'Reconnect-attempt failed ??\n'
+            )
+            await trio.sleep(0.2)  # throttle
+            raise berr
 
+        #|_ws & nursery block ends
         nobsws._connected = trio.Event()
         if cs.cancelled_caught:
             log.cancel(
@@ -324,21 +342,25 @@ async def open_autorecon_ws(
     connetivity errors, or some user defined recv timeout.
 
     You can provide a ``fixture`` async-context-manager which will be
-    entered/exitted around each connection reset; eg. for (re)requesting
-    subscriptions without requiring streaming setup code to rerun.
+    entered/exitted around each connection reset; eg. for
+    (re)requesting subscriptions without requiring streaming setup
+    code to rerun.
 
     '''
     snd: trio.MemorySendChannel
     rcv: trio.MemoryReceiveChannel
     snd, rcv = trio.open_memory_channel(616)
 
-    async with trio.open_nursery() as n:
+    async with (
+        tractor.trionics.collapse_eg(),
+        trio.open_nursery() as tn
+    ):
         nobsws = NoBsWs(
             url,
             rcv,
             msg_recv_timeout=msg_recv_timeout,
         )
-        await n.start(
+        await tn.start(
             partial(
                 _reconnect_forever,
                 url,
@@ -351,11 +373,10 @@ async def open_autorecon_ws(
         await nobsws._connected.wait()
         assert nobsws._cs
         assert nobsws.connected()
-
         try:
             yield nobsws
         finally:
-            n.cancel_scope.cancel()
+            tn.cancel_scope.cancel()
 
 
 '''
@@ -368,8 +389,8 @@ of msgs over a `NoBsWs`.
 class JSONRPCResult(Struct):
     id: int
     jsonrpc: str = '2.0'
-    result: Optional[dict] = None
-    error: Optional[dict] = None
+    result: dict|None = None
+    error: dict|None = None
 
 
 @acm