#### Why I did it
Adopt a single way to get fan direction for all ASIC types.
It depends on hw-mgmt V.7.0010.2000.2303. Depends on https://github.com/Azure/sonic-buildimage/pull/7419
#### How I did it
Originally, the get_direction was implemented by fetching and parsing `/var/run/hw-management/system/fan_dir` on the Spectrum-2 and the Spectrum-3 systems. It isn't supported on the Spectrum system.
Now, it is implemented by fetching `/var/run/hw-management/thermal/fanX_dir` for all the platforms.
Signed-off-by: Stephen Sun <stephens@nvidia.com>