Rename some parse failure tests to parse-fail-*

These were mistakenly labeled `eval-fail-*`.

Note that the `lang.sh` runner passes `parse-fail-*` tests on stdin, so
filenames are removed from error messages.

Change-Id: I7f3a0d78b6cfa87af29aaa1b7af19d5a57fd4ade

tests/functional/lang/parse-fail-eol-1.err.exp

@@ -1,5 +1,5 @@
 error: undefined variable 'invalid'
-       at /pwd/lang/eval-fail-eol-1.nix:2:1:
+       at «stdin»:2:1:
             1| # foo
             2| invalid
              | ^

tests/functional/lang/parse-fail-eol-2.err.exp

@@ -1,5 +1,5 @@
 error: undefined variable 'invalid'
-       at /pwd/lang/eval-fail-eol-2.nix:2:1:
+       at «stdin»:2:1:
             1| # foo
             2| invalid
              | ^

tests/functional/lang/parse-fail-eol-3.err.exp

@@ -1,5 +1,5 @@
 error: undefined variable 'invalid'
-       at /pwd/lang/eval-fail-eol-3.nix:2:1:
+       at «stdin»:2:1:
             1| # foo
             2| invalid
              | ^

tests/functional/lang/parse-fail-path-slash.err.exp

@@ -1,5 +1,5 @@
 error: path has a trailing slash
-       at /pwd/lang/eval-fail-path-slash.nix:6:12:
+       at «stdin»:6:12:
             5| # and https://nixos.org/nix-dev/2016-June/020829.html
             6| /nix/store/
              |            ^

tests/functional/lang/parse-fail-set.err.exp

@@ -1,5 +1,5 @@
 error: undefined variable 'x'
-       at /pwd/lang/eval-fail-set.nix:1:3:
+       at «stdin»:1:3:
             1| 8.x
              |   ^
             2|