Remove *.stream.* fragment from property prefixes

[tzolov]

• in SchemaRegistryClientProperties replace prefix from spring.cloud.cloud.schema-registry-client to spring.cloud.schema-registry-client.
• in AvroMessageConverterProperties replace prefix from spring.cloud.stream.schema.avro to spring.cloud.schema.avro.
• in SchemaServerProperties replace prefix from spring.cloud.stream.schema.server to spring.cloud.schema.server.

For backward compatibility ensure that that old property prefixes are still supported and automatically converted into the new one.