Allow update entities to update report progress with decimals

[emontnemery]

Background:

Updates are slow for some devices. One example is devices communicating via low bandwidth networks such as Zigbee which need quite a bit of time to transfer the firmware.

The update entities only supports reporting an integer update progress. This means that is can take quite a few minutes before an update progress updates on the Zigbee end. This makes the user think the update isn't working, or that the update has stalled.

To solve this problem, allow float values for the progress, with a max of 2-digit precision. For example, 0.15 %.

Proposal:

Extend the type of the in_progress property from bool | int | None to bool | float | int | None
Add a new property display_precision: int | None, with a default value of None to influence how the progress is displayed. If display_precision is None, the progress should be displayed without decimals.

[frenck]

This has been approved in the Core architectural meeting ✅

../Frenck