Support dual binding for http and https for test-proxy wrapper

[heaths]

See #4345 for more context, but basically we should be able to bind both http://0.0.0.0:0 and https://0.0.0.0:0 and listen for both. See .NET's implementation for an example. I don't think we have any need for http binding right now, so putting this on the backlog.

[heaths]

Alternatively, we do what Go does. I was looking at their implementation more thoroughly - I basically ported the code from Go to Rust originally, making only idiomatic changes as little as possible - but it wasn't readily apparent what it bound to:

1. https://github.com/Azure/azure-sdk-for-go/blob/3116ae9a1e61ecd3ffdcc51fdc8bf12fd25f67de/sdk/internal/recording/server.go#L437 ->
2. https://github.com/Azure/azure-sdk-for-go/blob/3d772e6e3fa71a3203831fef284e9b400eb55bc2/sdk/internal/recording/recording.go#L288-L290 ->
3. https://github.com/Azure/azure-sdk-for-go/blob/3d772e6e3fa71a3203831fef284e9b400eb55bc2/sdk/internal/recording/recording.go#L281-L286 ->
4. https://github.com/Azure/azure-sdk-for-go/blob/3d772e6e3fa71a3203831fef284e9b400eb55bc2/sdk/internal/recording/recording.go#L232 <- (default)
5. https://github.com/Azure/azure-sdk-for-go/blob/3d772e6e3fa71a3203831fef284e9b400eb55bc2/sdk/internal/recording/recording.go#L244-L249

So, by default it does bind to HTTPS but only with a single binding. If that's enough for Go, maybe it will suffice for Rust.

[heaths]

Though, because we rely on PROXY_MANUAL_START we might need to support both bindings. Then again, as @scbedd suggested, we could just always communicate with https://localhost:5001 even if it makes a request on our behalf to http. Probably easier. The main issue is what Proxy::existing() does, because we use that when PROXY_MANUAL_START=true in the CI.

[heaths]

We can pass 2 separate URLs for binding via command line switch or env var e.g., https://github.com/Azure/azure-sdk-for-net/blob/2a044b2970cd3688c393cfb559f4850cb085e85d/sdk/core/Azure.Core.TestFramework/src/TestProxy.cs#L79-L87