feat(tvix/eval): Validate closed formals

Validate "closed formals" (formal parameters without an ellipsis) via a
new ValidateClosedFormals op, which checks the arguments (in an attr set
at the top of the stack) against the formal parameters on the Lambda in
the current frame, and returns a new UnexpectedArgument error (including
the span of the formals themselves!!) if any arguments aren't allowed

Change-Id: Idcc47a59167a83be1832a6229f137d84e426c56c
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7002
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI

tvix/eval/src/opcode.rs

@@ -98,6 +98,12 @@ pub enum OpCode {
     OpAttrsTrySelect,
     OpHasAttr,
 
+    /// Throw an error if the attribute set at the top of the stack has any attributes
+    /// other than those listed in the formals of the current lambda
+    ///
+    /// Panics if the current frame is not a lambda with formals
+    OpValidateClosedFormals,
+
     // `with`-handling
     OpPushWith(StackIdx),
     OpPopWith,