[inferbo] Fix min of minmax and linear
Summary:
This diff corrects missing cases of `exact_min`.
```
min(c1 + min(d1, x), c2 + x)
= min(min(c1 + d1, c1 + x), c2 + x)
= min(c1 + d1, min(c1 + x, c2 + x))
= min(c1 + d1, min(c1, c2) + x)
= min(c1, c2) + min(c1 + d1 - min(c1, c2), x)
```
```
min(c1 - max(d1, x), c2 - x)
= min(c1 + min(-d1, -x), c2 - x)
= min(min(c1 - d1, c1 - x), c2 - x)
= min(c1 - d1, min(c1 - x, c2 - x))
= min(c1 - d1, min(c1, c2) - x)
= min(c1, c2) + min(c1 - d1 - min(c1, c2), -x)
= min(c1, c2) - max(min(c1, c2) - (c1 - d1), x)
```
Reviewed By: ezgicicek
Differential Revision: D16769307
fbshipit-source-id: 7bafd2ed6
Sungkeun Cho