Code quality: Fix header guards consistency

Adds `header_guards.sh` bash script, used in CI to validate future
changes. Can be run locally to fix invalid header guards.

tests/core/io/test_image.h

@@ -300,4 +300,5 @@ TEST_CASE("[Image] Modifying pixels of an image") {
 			"flip_y() should not leave old pixels behind.");
 }
 } // namespace TestImage
+
 #endif // TEST_IMAGE_H

tests/core/io/test_resource.h

@@ -28,8 +28,8 @@
 /* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
 /*************************************************************************/
 
-#ifndef TEST_RESOURCE
-#define TEST_RESOURCE
+#ifndef TEST_RESOURCE_H
+#define TEST_RESOURCE_H
 
 #include "core/io/resource.h"
 #include "core/io/resource_loader.h"
@@ -111,4 +111,4 @@ TEST_CASE("[Resource] Saving and loading") {
 }
 } // namespace TestResource
 
-#endif // TEST_RESOURCE
+#endif // TEST_RESOURCE_H

tests/core/math/test_basis.h

@@ -283,4 +283,4 @@ TEST_CASE("[Stress][Basis] Euler conversions") {
 }
 } // namespace TestBasis
 
-#endif
+#endif // TEST_BASIS_H

tests/core/templates/test_hash_set.h

@@ -225,4 +225,4 @@ TEST_CASE("[HashSet] Copy") {
 
 } // namespace TestHashSet
 
-#endif // TEST_HASH_MAP_H
+#endif // TEST_HASH_SET_H

tests/scene/test_path_3d.h

@@ -81,4 +81,4 @@ TEST_CASE("[Path3D] Curve setter and getter") {
 
 } // namespace TestPath3D
 
-#endif // TEST_PATH_3D
+#endif // TEST_PATH_3D_H

tests/servers/test_text_server.h

@@ -28,11 +28,11 @@
 /* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
 /*************************************************************************/
 
-#ifdef TOOLS_ENABLED
-
 #ifndef TEST_TEXT_SERVER_H
 #define TEST_TEXT_SERVER_H
 
+#ifdef TOOLS_ENABLED
+
 #include "editor/builtin_fonts.gen.h"
 #include "servers/text_server.h"
 #include "tests/test_macros.h"
@@ -561,5 +561,6 @@ TEST_SUITE("[[TextServer]") {
 }
 }; // namespace TestTextServer
 
-#endif // TEST_TEXT_SERVER_H
 #endif // TOOLS_ENABLED
+
+#endif // TEST_TEXT_SERVER_H