[EuiRange] Migrate from class to function component

`EuiRange` provides a single-handle range slider with optional tooltip, ticks, levels, and input field.

- **File:** `components/form/range/range.tsx`
- **Class size:** 293 lines
- **State:** `id`, `isPopoverOpen`, `trackWidth`
- **Lifecycle:** None

**Migration notes:**

No lifecycle methods despite size. State is simple. Complexity is in the input/slider coordination and tooltip positioning. Should be migrated together with or before `EuiDualRange`.

**Acceptance criteria:**

- [ ] Convert to function component with hooks
- [ ] Maintain slider/input coordination
- [ ] All existing tests pass