Refactoring of CPS Delta APIs

Refactoring of CPS Delta APIs

Refactoring of CPS delta APIs from two separate endpoints to a single endpoint.
  - GET: /v2/dataspaces/{dataspace-name}/anchors/{anchor-name}/deltaAnchors
  - POST: /v2/dataspaces/{dataspace-name}/anchors/{anchor-name}/deltaByPayload
To new endpoint can perform two operatios as follows:
  - GET: /v2/dataspaces/{dataspace-name}/anchors/{source-anchor-name}/delta
  - POST: /v2/dataspaces/{dataspace-name}/anchors/{source-anchor-name}/delta

Note: this patch only addresses the issue around refactoring of Delta
endpoint to a singular well defined endpoint. A separate patch will
be created to refactor the entire Delta feature out of CPS Data,
into a separate interface namely CPS Delta

Issue-ID: CPS-2310
Change-Id: Ic62c8308cf368b4378235597a11c476809a150b8
Signed-off-by: Arpit Singh <as00745003@techmahindra.com>