Reduce unnecessary COW on Vector by make writing explicit

This commit makes operator[] on Vector const and adds a write proxy to it.  From
now on writes to Vectors need to happen through the .write proxy. So for
instance:

Vector<int> vec;
vec.push_back(10);
std::cout << vec[0] << std::endl;
vec.write[0] = 20;

Failing to use the .write proxy will cause a compilation error.

In addition COWable datatypes can now embed a CowData pointer to their data.
This means that String, CharString, and VMap no longer use or derive from
Vector.

_ALWAYS_INLINE_ and _FORCE_INLINE_ are now equivalent for debug and non-debug
builds. This is a lot faster for Vector in the editor and while running tests.
The reason why this difference used to exist is because force-inlined methods
used to give a bad debugging experience. After extensive testing with modern
compilers this is no longer the case.

1 files changed, 2 insertions, 2 deletions

diff --git a/editor/plugins/animation_player_editor_plugin.cpp b/editor/plugins/animation_player_editor_plugin.cpp
index 23eeef9f20..9ab5436de8 100644
--- a/editor/plugins/animation_player_editor_plugin.cpp
+++ b/editor/plugins/animation_player_editor_plugin.cpp
@@ -1333,7 +1333,7 @@ void AnimationPlayerEditor::_allocate_onion_layers() {
 		bool is_present = onion.differences_only && i == captures - 1;
 
 		// Each capture is a viewport with a canvas item attached that renders a full-size rect with the contents of the main viewport
-		onion.captures[i] = VS::get_singleton()->viewport_create();
+		onion.captures.write[i] = VS::get_singleton()->viewport_create();
 		VS::get_singleton()->viewport_set_usage(onion.captures[i], VS::VIEWPORT_USAGE_2D);
 		VS::get_singleton()->viewport_set_size(onion.captures[i], capture_size.width, capture_size.height);
 		VS::get_singleton()->viewport_set_update_mode(onion.captures[i], VS::VIEWPORT_UPDATE_ALWAYS);
@@ -1473,7 +1473,7 @@ void AnimationPlayerEditor::_prepare_onion_layers_2() {
 		float pos = cpos + step_off * anim->get_step();
 
 		bool valid = anim->has_loop() || (pos >= 0 && pos <= anim->get_length());
-		onion.captures_valid[cidx] = valid;
+		onion.captures_valid.write[cidx] = valid;
 		if (valid) {
 			player->seek(pos, true);
 			get_tree()->flush_transform_notifications(); // Needed for transforms of Spatials