local.settings.json not injected/included into environment variables when using a FunctionsStartup class.

Azure Function V4 - Can be easily replicated using the template solution in visual studio 2019/2022.

When you create an Azure function and you update the `local.settings.json` Values array with properties you want to access via `Environment.GetEnvironmentVariables()` they are pulled through successfully with no issues.

If you however want to use DI and you add in a `FunctionsStartup `class `local.settings.json` no longer get injected/included within the Environment Variables.

Now I realize that you can work around this by implementing `IConfiguration`. However the Microsoft Documentation states that the benefit of using `GetEnvironmentVariables `is that if we set up access to a Key Vault, the relevant keys can be pulled from that using `GetEnvironmentVariables`, so we don't have to necessarily write code to do this. It's nice and neat.

So I am unsure if this is a bug, or if it is acting as intended. The behavior seems to run counter to the official documentation.