tests(f2/repl): migrate builtins_warn.test

Change-Id: Iaed1fb8651840b855ec7bdf5087681dc5eb9d54c

tests/functional2/repl_characterization/builtins/builtins_warn.md

@@ -0,0 +1,37 @@
+---
+args: ['--debugger', '--option', 'debugger-on-warn', 'true']
+---
+
+Enter debugger with debugger-on-warn set.
+
+```nix
+let inspect = v: builtins.warn "inspect is deprecated" (throw "this happens after"); in inspect { }
+```
+```output
+warning: inspect is deprecated
+warning: builtins.warn reached
+
+Added 2 variables.
+```
+
+
+Continue after the warn then breaks on the `throw`
+
+```nix
+:c
+```
+```output
+error: this happens after
+
+Added 2 variables.
+```
+
+
+Finally, continue after that error exits and prints the error
+```nix
+:c
+```
+```output
+error: this happens after
+
+```