mgmtd: Enroll Staticd as a backend client for MGMTD

mgmtd: Enroll Staticd as a backend client for MGMTD

This commmit introduces Staticd as a backend client for the MGMTd
framework. All the static commands will be diverted to the MGMT
daemon and will use the transactional model to make changes to the
internal state. Similar mechanism can be used by other daemons to use
the MGMT framework in the future.

This commit includes the following functionalities in the changeset:
1. Diverts all the staticd (config only) commands to MGMTd.
2. Enrolls staticd as a backend client to use the MGMT framework.
3. Modify the staticd NB config handlers so that they can be compiled
   into a library and loaded in the MGMTd process context.

Co-authored-by: Pushpasis Sarkar <pushpasis@gmail.com>
Co-authored-by: Abhinay Ramesh <rabhinay@vmware.com>
Co-authored-by: Ujwal P <ujwalp@vmware.com>
Signed-off-by: Yash Ranjan <ranjany@vmware.com>