feat(tazjin/presentations): bootstrap tvix-eval-2023 presentation

I spent way too much time fighting LaTeX to do roughly what I want
here again, but all the alternatives are even worse.

Change-Id: Ibe12a4ce175ceb73e9d6e276613dcd4827dd76c4
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9150
Autosubmit: tazjin <tazjin@tvl.su>
Reviewed-by: Mark Shevchenko <markshevchenko@gmail.com>
Tested-by: BuildkiteCI

users/tazjin/presentations/tvix-eval-2023/cppnix-example-smuggling.cpp

@@ -0,0 +1,12 @@
+struct Env {
+  Value * values[0];
+  // ... some more fields
+};
+
+// ....
+
+if (env->type == Env::HasWithExpr) {
+  Value * v = allocValue();
+  evalAttrs(*env->up, (Expr *) env->values[0], *v, noPos, "<borked>");
+  // ...
+}