tests/functional2/lang: add tests for NUL bytes in JSON and TOML

Based on the tests in the upstream PR.

Co-authored-by: Philipp Otterbein <potterbein@blockstream.com>
Upstream-PR: https://github.com/NixOS/nix/pull/12024
Change-Id: I6a6a69643ae9bd2445e551013d09e64ac1fe9916

tests/functional2/lang/nul_bytes_parsers/eval-allow-depr-fromJSON-value.out.exp

@@ -0,0 +1 @@
+"a"

tests/functional2/lang/nul_bytes_parsers/eval-allow-depr-fromTOML-value.out.exp

@@ -0,0 +1 @@
+{ k = "a"; }

tests/functional2/lang/nul_bytes_parsers/eval-depr-fromJSON-value.out.exp

@@ -0,0 +1 @@
+"a"

tests/functional2/lang/nul_bytes_parsers/eval-depr-fromTOML-value.out.exp

@@ -0,0 +1 @@
+{ k = "a"; }

tests/functional2/lang/nul_bytes_parsers/in-fromJSON-key.nix

@@ -0,0 +1 @@
+builtins.fromJSON ''{"a\u0000b": 1}''

tests/functional2/lang/nul_bytes_parsers/in-fromJSON-value.nix

@@ -0,0 +1 @@
+builtins.fromJSON ''"a\u0000b"''

tests/functional2/lang/nul_bytes_parsers/in-fromTOML-key.nix

@@ -0,0 +1 @@
+builtins.fromTOML ''"a\u0000b" = 1''

tests/functional2/lang/nul_bytes_parsers/in-fromTOML-value.nix

@@ -0,0 +1 @@
+builtins.fromTOML ''k = "a\u0000b"''

tests/functional2/lang/nul_bytes_parsers/test.toml

@@ -0,0 +1,11 @@
+[[test]]
+name = "eval-depr"
+matrix = true
+# FIXME: These should fail.
+runner = "eval-okay"
+
+[[test]]
+name = "eval-allow-depr"
+matrix = true
+runner = "eval-okay"
+flags = ["--extra-deprecated-features", "nul-bytes"]