Update xknx to 0.20.2

[marvin-w]

Proposed change

Bump XKNX to 0.20.2 and properly handle shutdown of devices.

Be aware: This was not an issue before as during reloading we would completely reinitialize the whole module.

But maybe we want to support dynamic entity loading at some point then this would have been bad.

https://github.com/XKNX/xknx/releases/tag/0.20.2 (for the diff just click diff to 0.20.1)

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[probot-home-assistant]

Hey there @Julius2342, @farmio, mind taking a look at this pull request as it has been labeled with an integration (knx) you are listed as a code owner for? Thanks!
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[frenck]

Should this go into a patch release?

[marvin-w]

Should this go into a patch release?

Yes, I tagged it

[marvin-w]

The test that got adjusted in this PR is from #69697 which is not part of 2022.4.*.

Do we need to tag this too since it's just tests or how do we proceed with that? If you just cherry-pick this it would most likely result in a failure.