This PR is just a quick house-cleaning PR that I've been meaning to do
for awhile. In the past, `installation_id` was called `device_id`. But
this name never reflected what it actually was - so we renamed it to
`installation_id`, but we kept the name as `device_id` in the
`kv_store`. I'm wanting to use the `device_id` key in the future, so to
keep things clearly labeled, I'm doing the key rename now.

Release Notes:

- N/A