Fix lost wakeups with stdin and wasip3 (#12711)

I've been running some tests with wasip3 recently and I was running into
a situation where a program would read stdin, get some data, and then
stdin w

Fix lost wakeups with stdin and wasip3 (#12711)

I've been running some tests with wasip3 recently and I was running into
a situation where a program would read stdin, get some data, and then
stdin would be closed. The second read of stdin wouldn't get a wakeup
and would get stuck forever despite stdin being closed. I'm not 100%
sure what was happening but I'm highly suspect of the `Notify`-based
synchronization here as I know historically that's a tricky primitive to
work with. This applies a hammer and moves some lock scopes up a bit
further to avoid dealing with trickiness and instead ensure everything
proceeds in lockstep.

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