feat(tvix/eval): Implement builtins.removeAttrs

Change-Id: I28910991a0108436a42ac7bf3458f9180a44154e
Reviewed-on: https://cl.tvl.fyi/c/depot/+/6928
Reviewed-by: Adam Joseph <adam@westernsemico.com>
Reviewed-by: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI

tvix/eval/src/tests/tvix_tests/eval-fail-remove.nix

@@ -0,0 +1,5 @@
+let {
+  attrs = {x = 123; y = 456;};
+
+  body = (removeAttrs attrs ["x"]).x;
+}