EV chargers and others: expose real time update switch/refresh button
- many devices have a dp that indicates "online" or
"offline". Originally this was implemented in many devices as a binary
sensor with class connectivity. This is not particularly useful, as if
a device is offline, it will not be able to communicate so it always
seemed strange to put such a dp on a device.
Over time, it has been discovered that these dps are actually
writable, and control the frequency of updates from the device.
- on devices where the dp was always reported, implement it as a
"Real time updates" switch
- on devices that do not always report it, implement it as a
"Refresh" button.
Usually, sending "online" will take effect for a limited period, and
need to be resent after a while.
Issue #4396