Rename some sizevars methods for clarity (#105585)
The guard functions require you to ALREADY KNOW that a particular
condition holds. If you don't know (you want to guard on an expression
being a particular value, and then get access to that value), use
the evaluate functions.
I renamed the functions that don't abide by this:
```
guard_min -> evaluate_min
guard_max (deleted, no uses)
guard_static_shape -> evaluate_static_shape
guard_static_shapes -> evaluate_static_shapes
```
Some added comments.
Signed-off-by: Edward Z. Yang <ezyang@meta.com>
Pull Request resolved: https://github.com/pytorch/pytorch/pull/105585
Approved by: https://github.com/voznesenskym
