refactor(tvix/eval): rename OpAttrsIsSet -> OpHasAttr

This matches the name of the AST node from which it was compiled.
Suggested by sterni in cl/6231

Change-Id: Ia51525158d2f47467c01fce2282005b1a8417a47
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6623
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
Reviewed-by: grfn <grfn@gws.fyi>

tvix/eval/src/vm.rs

@@ -317,7 +317,7 @@ impl<'o> VM<'o> {
                     self.push(value);
                 }
 
-                OpCode::OpAttrsIsSet => {
+                OpCode::OpHasAttr => {
                     let key = fallible!(self, self.pop().to_str());
                     let result = match self.pop() {
                         Value::Attrs(attrs) => attrs.contains(key.as_str()),