Support DAPR_HTTP_ENDPOINT and/or DAPR_GRPC_ENDPOINT

[artursouza]

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Describe the proposal

Allow consistent way to configure endpoint for Dapr's sidecar, while enabling remote sidecar configuration.

Child of https://github.com/dapr/dapr/issues/6035

SDK should parse these in a consistent way, so operators have a consistent environment variable to set for Dapr apps. Right now, each SDK has their own way of configuring the endpoint for Dapr's sidecar.

If SDK allows gRPC communication from SDK to sidecar, then DAPR_GRPC_ENDPOINT must be supported. If SDK allows HTTP communication from SDK to sidecar, then DAPR_HTTP_ENDPOINT must be supported. DAPR_HTTP_ENDPOINT and DAPR_GRPC_ENDPOINT and not exclusive, meaning it is acceptable to support both, like in the Java SDK, if the SDK supports both protocols. Also, companies might decide to offer different endpoints per protocol, so there is not an unique environment variable for both.