Move tests and sample formats to the top-level

I think this structure is a bit nicer, as it makes it easy for new-comers to see the current capabilities of the language.

Author: brendanzab

fathom/tests/source_tests.rs

@@ -7,8 +7,10 @@ use walkdir::WalkDir;
 fn main() {
     let args = libtest_mimic::Arguments::from_args();
 
+    std::env::set_current_dir("..").unwrap();
+
     let tests = std::iter::empty()
-        .chain(find_source_files("examples").map(extract_test))
+        .chain(find_source_files("formats").map(extract_test))
         .chain(find_source_files("tests").map(extract_test))
         .collect();
 

flake.nix

@@ -74,8 +74,8 @@
             (nix-filter.lib.inDirectory "fathom")
           ];
           exclude = [
-            (nix-filter.lib.inDirectory "fathom/examples")
-            (nix-filter.lib.inDirectory "fathom/test")
+            (nix-filter.lib.inDirectory "examples")
+            (nix-filter.lib.inDirectory "test")
           ];
         };
         crate-check-sources = nix-filter.lib.filter {