Mapper to group Subscription Details for DMI

- introduced a mapper to group a collection of subscription
  keys(datastore cmhandle and xpath ) based on datastore and xpath
- the information will be used to send out to the dmi plugin

Issue-ID: CPS-2312
Change-Id: I99f509eb5b4a8c3a7fb1078ae86490d894f22b6c
Signed-off-by: mpriyank <priyank.maheshwari@est.tech>
3 files changed