fix(tvix/eval): type check function argument with set pattern

C++ Nix forces and typechecks the passed argument even if it is not
necessary in order to compute the return value of the function. I
discovered this when I thought our formals miscompilation might be that
we are too strict, but doesn't look like it in this case.

Change-Id: Ifb3c92592293052c489d1e3ae8c7c54e4b6b4dc6
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8701
Tested-by: BuildkiteCI
Autosubmit: sterni <sternenseemann@systemli.org>
Reviewed-by: tazjin <tazjin@tvl.su>

tvix/eval/src/opcode.rs

@@ -129,6 +129,7 @@ pub enum OpCode {
 
     // Type assertion operators
     OpAssertBool,
+    OpAssertAttrs,
 
     /// Access local identifiers with statically known positions.
     OpGetLocal(StackIdx),