Enable binary support for WSClient

[meln5674]

What type of PR is this?

/kind feature

What this PR does / why we need it:

Currently, under python 3, the WSClient decodes all data via UTF-8. This will break, e.g. capturing the stdout of tar or gzip. This adds a new 'binary' kwarg to the WSClient class and websocket_call function. If this is set to true, then the decoding will not happen, and all channels will be interpreted as binary.
This does raise a slight complication, as the OpenAPI-generated client will convert the output to a string, no matter what, which it ends up doing by (effectively) calling repr(). This requires a bit of magic to recover the orignial bytes, and is inefficient. However, this is only the case when using the default _preload_content=True, when setting this to False and manually calling read_all or read_channel, this issue does not arise.

Which issue(s) this PR fixes:

Fixes #1471

Special notes for your reviewer:

Does this PR introduce a user-facing change?

Added 'binary' keyword argument to WSClient to use binary channels instead of string (utf8).

Additional documentation e.g., KEPs (Kubernetes Enhancement Proposals), usage docs, etc.:

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: meln5674 / name: Andrew Melnick (488518d)

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[roycaihw]

/assign @yliaog
/cc

[yliaog]

thanks for the PR

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: meln5674, yliaog

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