Rewrite HashMapHasherDefault based on type traits - it is now possible to declare a default hashing function for any type.

Remove cross-project includes from `hashfuncs.h`.
Improve hashing function for `Color` (based on values instead of `String`).
Move `Variant` comparison from `hash_map.h` to `dictionary.cpp` (`VariantComparatorDictionary`), where it's used.
Remove now unnecessary `HashableHasher`.

drivers/metal/inflection_map.h

@@ -33,6 +33,8 @@
 #include "core/templates/hash_map.h"
 #include "core/templates/local_vector.h"
 
+#include <iterator>
+
 /// An unordered map that splits elements between a fast-access vector of LinearCount consecutively
 /// indexed elements, and a slower-access map holding sparse indexes larger than LinearCount.
 ///

drivers/metal/metal_objects.h

@@ -196,7 +196,7 @@ public:
 
 class API_AVAILABLE(macos(11.0), ios(14.0), tvos(14.0)) MDResourceCache {
 private:
-	typedef HashMap<ClearAttKey, id<MTLRenderPipelineState>, HashableHasher<ClearAttKey>> HashMap;
+	typedef HashMap<ClearAttKey, id<MTLRenderPipelineState>> HashMap;
 	std::unique_ptr<MDResourceFactory> resource_factory;
 	HashMap clear_states;
 

drivers/metal/pixel_formats.h

@@ -60,6 +60,7 @@ GODOT_CLANG_WARNING_PUSH_AND_IGNORE("-Wdeprecated-declarations")
 #include "servers/rendering/rendering_device.h"
 
 #import <Metal/Metal.h>
+#include <iterator>
 
 #pragma mark -
 #pragma mark Metal format capabilities

drivers/metal/rendering_device_driver_metal.h

@@ -90,7 +90,7 @@ class API_AVAILABLE(macos(11.0), ios(14.0), tvos(14.0)) RenderingDeviceDriverMet
 	 * To prevent unbounded growth of the cache, cache entries are automatically freed when
 	 * there are no more references to the MDLibrary associated with the cache entry.
 	 */
-	HashMap<SHA256Digest, ShaderCacheEntry *, HashableHasher<SHA256Digest>> _shader_cache;
+	HashMap<SHA256Digest, ShaderCacheEntry *> _shader_cache;
 	void shader_cache_free_entry(const SHA256Digest &key);
 
 public: