This PR reduces noise in the 'Equivalence classes' section of the
`grind` diagnostics. It now uses a notion of *support expressions*.
Right now, it is hard-coded, but we will probably make it extensible in
the future. The current definition is
- `match`, `ite` and `dite`-applications. They have builtin support in
`grind`.
- Cast-like applications used by `grind`: `toQ`, `toInt`, `Nat.cast`,
`Int.cast`, and `cast`
- `grind` gadget applications (e.g., `Grind.nestedDecidable`)
- Projections of constructors (e.g., `{ x := 1, y := 2}.x`)
- Auxiliary arithmetic terms constructed by solvers such as `cutsat` and
`ring`.
If an equivalence class contains at most one non-support term, it goes
into the “others” bucket. Otherwise, we display the non-support elements
and place the support terms in a child node.
**BEFORE**:
<img width="1397" height="1558" alt="image"
src="https://github.com/user-attachments/assets/4fd4de31-7300-4158-908b-247024381243"
/>
**AFTER**:
<img width="840" height="340" alt="image"
src="https://github.com/user-attachments/assets/05020f34-4ade-49bf-8ccc-9eb0ba53c861"
/>
**Remark**: No information is lost; it is just grouped differently."
c6abc3c036