Created new test_runner.c and test_.py

This is to try a different design for testing, the goals are to make the
test infrastructure a bit simpler, with clear stages for building and
running, and faster, by avoiding rebuilding lfs.c n-times.

runners/test_runner.h

@@ -0,0 +1,26 @@
+#ifndef TEST_RUNNER_H
+#define TEST_RUNNER_H
+
+#include "lfs.h"
+
+
+struct test_case {
+    const char *id;
+    const char *name;
+    const char *path;
+    uint32_t permutations;
+    void (*run)(struct lfs_config *cfg, uint32_t perm);
+};
+
+struct test_suite {
+    const char *id;
+    const char *name;
+    const char *path;
+    const struct test_case *const *cases;
+    size_t case_count;
+};
+
+extern const struct test_suite *test_suites[];
+extern const size_t test_suite_count;
+
+#endif