Introduce golden file mechanism for tests

v0/tests/log_on_line.txt

@@ -0,0 +1,4 @@
+--- test.c ---
+1| int main() []
+              ^^
+   unexpected token

v0/tests/log_on_line_variadic.txt

@@ -0,0 +1,4 @@
+--- test.c ---
+1| int main() []
+              ^^
+   unexpected token 'x'

v0/tests/unknown_token.txt

@@ -0,0 +1,4 @@
+--- test.c ---
+1| %
+   ^
+   unexpected token '%'