[Arith] Add constraint visitor snapshots

[tlopex]

Some TIR analyses need to collect arithmetic premises at one IR location and replay them at another. The existing analyzer scope is tied to the traversal lifetime and cannot retain multiple independent snapshots.

This change adds ConstrVisitor and ConstrSet to collect supported scalar predicates, bindings, and ranges while visiting TIR. Snapshots can outlive the visitor, be renamed for different executions, merged as conjunctions, and replayed through the arithmetic analyzer.

Unsupported or side-effecting expressions are discarded conservatively, so omitted facts only weaken proofs. The visitor handles branches, loops, let bindings, Bind/AssertStmt, reduction initialization scopes, and if_then_else.

This is adapted from TileLang: https://github.com/tile-ai/tilelang/blob/main/src/transform/common/constr_visitor.h