[lib] deprecate sendDMOperation and implement method to create sending promise

Summary:
ENG-8423.

We still need promise to be resolved after sending messages, but generating messages was moved to processDMOps.

Returning promise to later in that stack put it to dispatchActionPromise.

useProcessAndSendDMOperation looks no obsolete, but will be updated later in the stack.

Depends on D13150

Test Plan:
Call getDMOpsSendingPromise and check if it works.

Note: This stack is tested end-to-end according to the process described here.

Reviewers: tomek, inka

Reviewed By: tomek

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D13151