Added restService based overload with CachedSchemaRegistryClient

[DwivediPrasoon]

related to issue: #364

Basic auth doesn't seem to connect to Schema registry on CC using the basic auth method i.e.

AbrisConfig.fromConfluentAvro.downloadReaderSchemaByLatestVersion
          .andTopicNameStrategy(getTopic)
          .usingSchemaRegistry(
            Map(
              AbrisConfig.SCHEMA_REGISTRY_URL -> Configuration.schemaRegistryUrl,
              SchemaRegistryClientConfig.BASIC_AUTH_CREDENTIALS_SOURCE -> "USER_INFO",
              SchemaRegistryClientConfig.USER_INFO_CONFIG -> s"${Configuration.schemaRegistryUsername}:${Configuration.schemaRegistryPassword}"
            )
          )

but able to connect when used with restService constructor of CachedSchemaRegistryClient. This PR aims at giving an option to pass RestService object to be able to create CachedSchemaRegistryClient for it.

[veenaypatil]

1. Lets update the files where this class is being used.
2. Add Test cases
3. Add scaladoc for this in terms of how to use this constructor