Convert client wrappers to coroutines, use thread pools for actual calls

[nolar]

Issue : #142

Description

The client wrappers are used to isolate the framework's reactor from the specific HTTPS API calls needed to talk to Kubernetes, and from the ways of doing so. They provide a limited set of operations needed only, and no more than that (no general-purpose DSL for resource manipulation).

In this PR, all remaining synchronous client wrappers are converted to async coroutines, while they remain Pykube-based internally (pykube-ng is synchronous, as requests are synchronous).

This is needed both for the switch to aiohttp (e.g. #176), and for the re-authentication activities (few issues).

The synchronous calls are moved few levels down the stack, and put into the thread-pool executors.

Previously, these calls were sync inside of the async event loop, so they were blocking. It was not a big problem, as most of them are executed only once or twice per run in the very beginning; the frequent resource-watching & resource-patching & event-posting calls were already executed in the thread pools. But it now becomes a problem since all API calling methods cannot be so diverse anymore, and have to be uniform (specifically, async).

Types of Changes

• Refactor/improvements

[zincr]

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[zincr]

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✅ Large Commits
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Approvals

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• ✅ Approved by PR author @nolar
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[nolar]

Zincr-bot, ping.