[Fix] _conv_flops_compute when padding is a str and stride=1 (#3169)
* fix conv_flops_compute when padding is a str when stride=1
* fix error
* change type of paddings to tuple
* fix padding calculation
* apply formatting check
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Co-authored-by: Cheng Li <pistasable@gmail.com>
Co-authored-by: Olatunji Ruwase <olruwase@microsoft.com>