Attempt to introduce graceful close from workers back to coordinator

[NHDaly]

Merges into #151.

[NHDaly]

@nickrobinson251 but this doesn't seem to be quite right either. With this change, now the tests are hanging; i'm not yet sure why.
Looks like it was stuck in the wait(w) at the end of close(w; from):

ERROR: LoadError: InterruptException:
Stacktrace:
  [1] try_yieldto(undo::typeof(Base.ensure_rescheduled))
    @ Base ./task.jl:931
  [2] wait()
    @ Base ./task.jl:995
  [3] wait(c::Base.GenericCondition{Base.Threads.SpinLock}; first::Bool)
    @ Base ./condition.jl:130
  [4] wait
    @ ./condition.jl:125 [inlined]
  [5] _wait(t::Task)
    @ Base ./task.jl:310
  [6] wait
    @ ./task.jl:350 [inlined]
  [7] fetch
    @ ./task.jl:372 [inlined]
  [8] wait(w::Worker)
    @ ReTestItems.Workers ~/.julia/dev/ReTestItems/src/workers.jl:128
  [9] close(w::Worker, from::Symbol)
    @ ReTestItems.Workers ~/.julia/dev/ReTestItems/src/workers.jl:123
 [10] close(w::Worker)
    @ ReTestItems.Workers ~/.julia/dev/ReTestItems/src/workers.jl:115
 [11] macro expansion
    @ ~/.julia/dev/ReTestItems/test/workers.jl:18 [inlined]
 [12] macro expansion
    @ ~/builds/julia-RAI/usr/share/julia/stdlib/v1.10/Test/src/Test.jl:1577 [inlined]

not sure why, but gotta run now. 👋

[NHDaly]

Closing in favor of #155.