Using environment variable for dapr sidecar host and using localhost instead of 127.0.0.1 as DAPR default sidecar host

[ondmal]

Description

• retrieve default value of DAPR sidecar host from DAPR_HOST environment variable
• use localhost instead of 127.0.0.1 as DAPR sidecar host default value if the environment variable is not specified

Issue reference

This PR will close: #1032

[ondmal]

One thing to consider.

WorkflowServiceCollectionExtensions class uses method TryGetGrpcAddress to validate the default GRPC endpoint and uses empty string if it is not well formed URI.

Maybe we should either validate the endpoint address when constructing the default (in DaprDefaults) or do not validate it at all (in WorkflowServiceCollectionExtensions).

In DaprDefaults we can use "localhost" and default port when the values in the environment variables are invalid to ensure that the default endpoint address will always be valid URI.

[artursouza]

This impacts this PR.