Add HTTP Client Factory into Java SDK

[alicejgibbons]

As we do in Dotnet today, it would be nice to give users the option to create an HTTP Client via the Java SDK through a factory. This would remove the current encapsulation around the existing invokeMethod and allow users additional options for HTTP Client without having to have all the method overloads.

For example in Dotnet:

var httpClient = DaprClient.CreateInvokeHttpClient();
var response = await httpClient.PostAsJsonAsync("http://order-processor/orders", order);

In the past we simplified this and now there is only HTTP for methodInvoke() and waitForSidecar(), but would be nice to standardize the SDKs: #1051