Backport https://github.com/Azure/sonic-buildimage/pull/9259 to 202012
#### Why I did it
Nvidia platform API does not support set LED to orange.
#### How I did it
Allow user to set LED to orange
#### How to verify it
Manual test
- Why I did it
The existing Fan led and Psu led object initialize itself to green color in init method. However, there are multiple daemons calls sonic platform API and there could be a case that:
A PSU is removed from system
Reboot switch
psud detects that 1 PSU is missing and set PSU led to red
Other daemon just start up and call sonic platform API, the API set PSU led to green by call PsuLed.init
This PR is a partial fix for the issue. As we also need guarantee that the led is initialized with a correct value. I checked existing psud and thermalctld code. psud always initialize the PSU led color on boot up, thermalcltd need some changes to initialize led color on the first run
- How I did it
Remove the led color initialization code from FanLed.init and PsuLed.init
- How to verify it
Manual test
System health feature needs to set/get system led status
- Add a led object in chassis class and initialize it when the API is called on host side
- Read/write system led system fs to get/set the status
