Move test resources to a common directory

All the external resources used by the tests are now placed inside the
common 'tests/resources' directory.

Signed-off-by: Vicent Marti <tanoku@gmail.com>

tests/t0402-details.c

@@ -6,7 +6,7 @@
 #include <git/commit.h>
 #include <git/revwalk.h>
 
-static const char *odb_dir = "../t0501-objects";
+static const char *odb_dir = "../resources/sample-odb";
 static const char *commit_ids[] = {
 	"a4a7dce85cf63874e984719f4fdd239f5145052f", /* 0 */
 	"9fd738e8f7967c078dceed8190330fc8648ee56a", /* 1 */

tests/t0501-walk.c

@@ -6,7 +6,7 @@
 #include <git/commit.h>
 #include <git/revwalk.h>
 
-static const char *odb_dir = "../t0501-objects";
+static const char *odb_dir = "../resources/sample-odb";
 /*
 	$ git log --oneline --graph --decorate
 	*   a4a7dce (HEAD, br2) Merge branch 'master' into br2