#### Why I did it
According to thermalctld hld, each fan must belong to a fan drawer, if the fan drawer does not physically exist, put fan into a virtual fan drawer. This PR is to clear fan from chassis._fan_list
#### How I did it
1. Don't put fan to chassis._fan_list
2. Always query fan from fan_drawer
**- Why I did it**
After migrating to python3, the operator '/' always get a float result, but it gets integer result in python2. Need fix this in thermal_conditions.
**- How I did it**
1. cast float value to int
2. change the unit test case to cover this situation
**- How to verify it**
Manually test and regression test
In order to support SONiC physical entity mib extension, a few new platform API are added to sonic-platform-common, this PR is to provide an mellanox platform implementation for those new APIs.
* [thermal control] Fix pmon docker stop issue on 3800
* [thermal fix] Fix QA test issue
* [thermal fix] change psu._get_power_available_status to psu.get_power_available_status
* [thermal fix] adjust log for PSU absence and power absence
* [thermal fix] add unit test for loading thermal policy file with duplicate conditions in different policies
* [thermal] fix fan.get_presence for non-removable SKU
* [thermal fix] fix issue: fan direction is based on drawer
* Fix issue: when fan is not present, should not read fan direction from sysfs but directly return N/A
* [thermal fix] add unit test for get_direction for absent FAN
* Unplugable PSU has no FAN, no need add a FAN object for this PSU
* Update submodules
Co-authored-by: Stephen Sun <5379172+stephenxs@users.noreply.github.com>
