Sdbusplus-based Shared Library

[Patrick Venture]

We have a lot of duplication across daemons using sdbusplus, and no
new utility library.  To avoid every daemon having their own timer
object, and their own this or that, I suggest we create this shared
library.

Thoughts?  We can start simple, just have a timer object in there, and
then the new timers being introduced to phosphor-hwmon and
phosphor-host-ipmid can be the first customers.

Patrick