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/rules.rs

@@ -368,7 +368,8 @@ impl<'a> Compiler<'a> {
                                     self.expect_binding_plan_for_expr(arg, &context_desc)?;
 
                                 if let BindingPlan::Parameter { .. } = &binding_plan {
-                                    self.apply_binding_plan(&binding_plan, param_reg, arg.span())
+                                    let _ = self
+                                        .apply_binding_plan(&binding_plan, param_reg, arg.span())
                                         .map_err(|e| CompilerError::from(e).at(arg.span()))?;
                                 } else {
                                     return Err(CompilerError::UnexpectedBindingPlan {