feat: Soft-assert mode for builtin out-params under not

- Add a scoped soft_assert_mode to the compiler so `not` statements compile their subexpressions without emitting hard AssertCondition/AssertNotUndefined instructions.
- Teach binding-plan application to return an optional result register; equality plans now yield a boolean in soft mode, allowing not abs(-5 , 3) to succeed instead of aborting.
- Update function-call, loop, and rule plumbing to consume the new binding-plan outcome, including copying the produced register when an out-parameter equality is used.
- Trim the OPA TODO list to the remaining troublesome folders.

Signed-off-by: Anand Krishnamoorthi <anakrish@microsoft.com>

src/languages/rego/compiler/loops.rs

@@ -249,7 +249,8 @@ impl<'a> Compiler<'a> {
         let body_start = self.program.instructions.len() as u16;
 
         if let Some((binding_plan, plan_span)) = key_binding_plan.as_ref() {
-            self.apply_binding_plan(binding_plan, key_reg, plan_span)
+            let _ = self
+                .apply_binding_plan(binding_plan, key_reg, plan_span)
                 .map_err(|e| CompilerError::from(e).at(plan_span))?;
         }