Fix maxsize in process, task and thread

[charlielito]

This should solve this #64 and also this #55 as this bug still there also for process.

I haven't fix sync because the structure is different, but there are also hardcoded maxsize=0 like here https://github.com/cgarciae/pypeln/blob/master/pypeln/sync/stage.py#L93 How should this be fixed?

Would be nice to have tests for this

[codecov-io]

Codecov Report

Merging #66 (5d67864) into master (a93a9c4) will increase coverage by 0.20%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #66      +/-   ##
==========================================
+ Coverage   90.57%   90.77%   +0.20%     
==========================================
  Files          61       61              
  Lines        2100     2114      +14     
==========================================
+ Hits         1902     1919      +17     
+ Misses        198      195       -3     

Impacted Files	Coverage Δ
pypeln/task/supervisor.py	97.22% <ø> (+2.77%)	⬆️
pypeln/process/stage.py	100.00% <100.00%> (ø)
pypeln/task/stage.py	98.33% <100.00%> (ø)
pypeln/task/utils.py	100.00% <100.00%> (ø)
pypeln/task/worker.py	95.89% <100.00%> (+1.44%)	⬆️
pypeln/thread/queue.py	96.15% <100.00%> (+0.37%)	⬆️
pypeln/thread/stage.py	100.00% <100.00%> (ø)
pypeln/thread/supervisor.py	100.00% <100.00%> (ø)

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[cgarciae]

maxsize does not make sense in sync because there is no concurrency, everything is implemented as an iterator but parameters are kept for API compatibility (you should be able to switch between any module without changes).

[cgarciae]

LGTM!

I discovered some areas of improvement while creating a test for this, the thread and task Workers / Supervisors got stuck if they weren't finished but being stopped by the GC. I created a short-term fix here but the solution involves having the done() methods not having to push DONE elements to the queue because put can block. Will open a separate PR.