tests/functional2/lang: Migrate trivial eval-fail tests

All changes are uniform and done with the same script, so checking only
some should suffice. For that reason, any tests involving multiple files
or custom CLI flags are not included in this commit.

Change-Id: Ib2d0e08937b56e241d99771a58aad34ed3ad308a

tests/functional2/lang/flake-ref-to-string-negative-integer/eval-fail.err.exp

@@ -0,0 +1,14 @@
+error:
+       … while calling the 'seq' builtin
+         at /pwd/in.nix:1:16:
+            1| let n = -1; in builtins.seq n (builtins.flakeRefToString {
+             |                ^
+            2|   type  = "github";
+
+       … while calling the 'flakeRefToString' builtin
+         at /pwd/in.nix:1:32:
+            1| let n = -1; in builtins.seq n (builtins.flakeRefToString {
+             |                                ^
+            2|   type  = "github";
+
+       error: negative value given for flake ref attr repo: -1