dbr quant overhead[2/x]: precalculate op_convert_info (#68347)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/68347
Moves `op_convert_info` to be precalculated in the convert step
instead of calculated dynamically. This should help with framework
overhead.
Test Plan:
Noisy benchmark:
```
// before
fp32: 0.016103 seconds avg
fx_prepared: 0.019841 seconds avg, 0.811601 speedup vs fp32
fx_quantized: 0.011907 seconds avg, 1.352346 speedup vs fp32
dt_prepared: 0.035055 seconds avg, 0.459357 speedup vs fp32
dt_quantized: 0.018891 seconds avg, 0.852417 speedup vs fp32
// after
fp32: 0.020535 seconds avg
fx_prepared: 0.023071 seconds avg, 0.890070 speedup vs fp32
fx_quantized: 0.011693 seconds avg, 1.756206 speedup vs fp32
dt_prepared: 0.038691 seconds avg, 0.530734 speedup vs fp32
dt_quantized: 0.021109 seconds avg, 0.972793 speedup vs fp32
```
The benchmark is too noisy to rely on, but according to `cProfiler`
this removes about 5% of overhead.
Reviewed By: jerryzh168
Differential Revision: D32463761
Pulled By: vkuzo
fbshipit-source-id: e2ad0d7eeff7dbadf3aa379604bfe9bec0c228fe
