cync_lan (Home Assistant custom_component) v2.6.0

The indicator LED is no longer experimental. It has been confirmed working
on real hardware, so it is out from behind the opt-in.

The Select, Number and Switch entities for indicator-LED mode, colour,
brightness and blink-on-disconnect already appeared by default - that part was
already right. What changed is the action: it is now cync_lan.set_indicator_led
rather than cync_lan.experimental_set_indicator_led, and it is registered
whether or not experimental commands are enabled.

The old name still works. It was the only name for several releases, so it
is in people's automations, and renaming without an alias would break them
silently - the symptom being a light that does not respond, which nobody traces
back to a service rename. Calling the old name logs a warning asking you to
update, and otherwise behaves identically.

Everything else stays behind the opt-in. Of the 27 experimental commands this
integration implements, this is the only one confirmed against real hardware;
the other 26 still send a cmd_code predicted from a length formula, which is
exactly what the gate is there to protect people from.