* Fix turn_on ignoring transition=0 and brightness=None, add test
This fixes light.turn_on for ZHA lights ignoring a transition of 0 when no brightness is given at the same time.
It also adds a test for that case.
Fixes https://github.com/home-assistant/core/issues/93265
* Add test for "force on" lights
This test checks that "force on" lights also get an "on" command (in addition to the "move to level" command) when turn_on is called with only transition=0.
* Fix "on" command sent for transition=0 calls, fix FORCE_ON missing for transition=0
This fixes an issue where the "on" command is sent in addition to a "move_to_level_with_on_off" command, even though the latter one is enough (for non-FORCE_ON lights).
It also fixes the test to not expect the unnecessary "on" command (in addition to the expected "move_to_level_with_on_off" command).
The `brightness != 0` change is needed to fix an issue where FORCE_ON lights did not get the required "on" command (in addition to "move_to_level_with_on_off") if turn_on was called with only transition=0.
(It could have been `brightness not None`, but that would also send an "on" command if turn_on is called with brightness=0 which HA somewhat "supports". The brightness != 0 check avoids that issue.)
* Improve comments in ZHA light class
bae5a3dbd6