Create cmdlet to retrieve the Functions Host runtime version

### Description

Create cmdlet to retrieve the Functions Host runtime version. For more information, please see [How do I check the functions runtime version?](https://github.com/Azure/azure-functions-host/wiki/How-do-I-check-the-functions-runtime-version%3F)

### Issue script & Debug output

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### Environment data

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### Module versions

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### Error output

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Start with the linked “How do I check the functions runtime version?” wiki page to determine the expected source and output for the Functions Host runtime version. Then locate the Azure PowerShell cmdlet area for the relevant Functions service and its tests; done means a documented cmdlet retrieves and exposes that version with coverage for the expected result.

Written by the indexing model from the issue text.