Rearrange aggregates response schema into one file

After removing v3 schemas, we have only 1 set of schemas for v2 (/v2.1)
APIs but those end up in scattered structure.

Schema files needs to be re arranged into a clean structure. Any
resource schema should be defined in single file for better readability.

This patch merges the aggregates response schema into one file.

Partially implements blueprint rearrange-nova-response-schemas
Change-Id: I2a173792fc83887635051477c312cba986a7f907
3 files changed