Support DAPR_HTTP_ENDPOINT and/or DAPR_GRPC_ENDPOINT

## 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.

Nell’issue non sono nominati file o test. Inizia ispezionando la configurazione esistente dell’endpoint sidecar dell’C++ SDK e i relativi punti di ingresso HTTP e gRPC, quindi traccia il modo in cui vengono lette le variabili d’ambiente. Il lavoro è completato quando le variabili supportate specifiche del protocollo configurano l’endpoint sidecar corrispondente, inclusi valori separati per HTTP e gRPC quando entrambi sono disponibili.

Scritto dal modello di indicizzazione a partire dal testo della issue.