stream+ws_client: Optional capture-all

[rawler]

This PR is a proposal to fix kubernetes-client/python#1013.

The fix is two-fold:

1. Improve the way WSClient._all is appended to, to avoid exponential slow-down.
2. Allow optional disabling of the "capture-all" behavior, to remove memory-usage altogether

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[rawler]

Side-note; As a user of the stream-API, the usage is not immediately clear, and it's also a bit inflexible. (Stdout is not necessarily characters?) I think this has room for some breaking API-improvements;

• Adding clarity to what kwargs and I can and cannot specify - stream() kwargs should be explicit and documented
• Supporting binary stdin/out. I had to work around this by use of base64. The data received seems to be bytes, the utf8-assumption is done in

  python-base/stream/ws_client.py

  Line 190 in a2d1024

  data = data.decode("utf-8", "replace")

• Buffering _all could potentially be a composed opt-in, rather than a default-integrated behavior.

I made a short attempt to add explicit **kwargs (which could be non-breaking), but it snowballed into scope-creep, and I realized I don't know the code well enough to feel comfortable making such changes.

[rawler]

I signed it

[rawler]

/assign @mbohlool

[codecov-io]

Codecov Report

Merging #178 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #178   +/-   ##
=======================================
  Coverage   93.41%   93.41%           
=======================================
  Files          13       13           
  Lines        1398     1398           
=======================================
  Hits         1306     1306           
  Misses         92       92

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[roycaihw]

/assign

[roycaihw]

/lgtm
/approve

Thanks for the improvement!

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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: rawler, roycaihw

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