Add execute custom command service to Overkiz

[iMicknl]

Proposed change

This PR adds the possibility to execute a custom command on the chosen Overkiz device. Overkiz devices often support many different features, which cannot always be mapped to specific Home Assistant entity features. This will also allow users to test unsupported features and/or unlock advanced device features.

Including exception handling, if the gateway responds that a command is not supported by the device.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Deprecation (breaking change to happen in the future)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue:
• Link to documentation pull request:

Checklist

• The code change is tested and works locally.
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• The code has been formatted using Ruff (ruff format homeassistant tests)
• Tests have been added to verify that the new code works.

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated for www.home-assistant.io

If the code communicates with devices, web services, or third-party tools:

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  Updated and included derived files by running: python3 -m script.hassfest.
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[home-assistant]

Hey there @vlebourl, @tetienne, @nyroDev, @Tronix117, @alexfp14, mind taking a look at this pull request as it has been labeled with an integration (overkiz) you are listed as a code owner for? Thanks!

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[iMicknl]

This is very very ugly, but I couldn't find a helper to retrieve the actual entity from the RegistryEntity. I need to retrieve my coordinator from my entity, otherwise for users with 2 Config Entries, this service call might run on the wrong config entry...

Any advice is appreciated!