Make fetch/wait on Task more like Future/RemoteChannel

[iamed2]

This implements #25928

[iamed2]

There were some uses of wait that I didn't catch when running tests locally; I just need to fix those.

[iamed2]

I can fix all of these but it would be nice to know why this happens:

      From worker 9:	ERROR (unhandled task failure): `wait(t::Task)` is deprecated, use `fetch(t)` instead.
      From worker 9:	Stacktrace:
      From worker 9:	 [1] depwarn(::String, ::Symbol) at ./deprecated.jl:68
      From worker 9:	 [2] wait(::Task) at ./deprecated.jl:56
      From worker 9:	 [3] macro expansion at /tmp/julia/share/julia/test/socket.jl:242 [inlined]
      From worker 9:	 [4] (::getfield(Main.Test71Main_socket, Symbol("##13#17")))() at ./task.jl:343

Deprecations shouldn't cause failures, right?

Never mind, found --depwarn=error

[JeffBezanson]

Looks like there is one more use to update in examples/embedding/embedding-test.jl.