Here I was thinking the bcaster (usage) maybe required a rework but,
NOPE it's just bc a checkpoint was needed in the parent task owning the
`tn` which spawns `get_sub_and_pull()` tasks to ensure the bg allocated
`an`/portal is eventually cancel-called..
Ah well, at least i started a patch for `MsgStream.subscribe()` to make
it multicast revertible.. XD
Anyway, I tossed in some checks & notes related to all that unnecessary
effort since I do think i'll move forward implementing it:
- for the `cache_hit` case always verify that the `bcast` clone is
unregistered from the common state subs after
`.subscribe().__aexit__()`.
- do a light check that the implicit `MsgStream._broadcaster` is always
the only bcrx instance left-leaked into that state.. that is until
i get the proper de-allocation/reversion from multicast -> unicast
working.
- put in mega detailed note about the required parent-task checkpoint.