Run python integration tests in parallel

[fresh-borzoni]

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• I searched in the issues and found nothing similar.

Description

We should use pytest-xdist to run several testing shards in parallel.
Currently single client tests run in 40-50s, we can probably do better with this.

So we just need proper setup for the whole suit, cleanup, use different data for each sub-suite and pytest-xdist to parallelise.

Willingness to contribute

• I'm willing to submit a PR!