[lib][tipc] Add helpers to simplify implementing event loops

This CL adds APIs to simplify implementation of event loops on top
of handle sets:

    tipc_hset_add_entry() - adds handle with associated event handler
                            to specified handle set
    tipc_hset_mod_entry() - modifies attributes (like event mask) for
                            handle previously attached to handle set
    tipc_hset_remove_entry() - removes specified handle form handle set
    tipc_handle_event() - wait on specified handle set and handle single
    tipc_run_event_loop() - run endless event loop

Bug: 134153462
Change-Id: Ib19dbe9c6454098992caadfa7fe7eb82339987b6
3 files changed