Refactored a handful of things in tests

- Now test errors have correct line reporting! #line directives
  are passed to the compiler that reference the relevant line in
  the test case shell script.

  --- Multi-block directory ---
  ./tests/test_dirs.sh:109: assert failed with 0, expected 1
      lfs_unmount(&lfs) => 1

- Cleaned up the number of implicit global variables provided to
  tests. A lot of these were infrequently used and made it difficult
  to remember what was provided. This isn't an MCU, so there's very
  little cost to stack allocations when needed.

- Minimized the results.py script (previously stats.py) output to
  match minimization of test output.

tests/test_format.sh

@@ -1,5 +1,7 @@
 #!/bin/bash
 set -eu
+export TEST_FILE=$0
+trap 'export TEST_LINE=$LINENO' DEBUG
 
 echo "=== Formatting tests ==="
 rm -rf blocks
@@ -46,5 +48,4 @@ scripts/test.py << TEST
     lfs_unmount(&lfs) => 0;
 TEST
 
-echo "--- Results ---"
-scripts/stats.py
+scripts/results.py