More readable Z3 expressions printer. (#106643)
This PR makes Z3 expressions easier to read and understand by creating a custom printer
for them.
Z3 expressions can be printed in 2 forms:
1. Using the builtin `str(e)` function
2. Using the `e.sexpr()` method
Problem is that (1) is a bit hard to read because its line breaks are not so
intuitive. (2) is a bit nicer, but the `to_int` and `to_real` functions clutter things up.
The custom printer is an improved `sexpr()` function:
- Leaves everything in one line
- Gets rid of `to_int` and `to_real` functions
- Reconstruct the floor division operations
- Merge commutative operation chains
Pull Request resolved: https://github.com/pytorch/pytorch/pull/106643
Approved by: https://github.com/ezyang
