Fix icons colors for files and directories at light color preset

[Scrawach]

• Fixes: [4.6.1-stable] Icons for files and directories in the file browser have messed up colors when you use the light color preset #116467

Before	After

After #111212 some icons are been lost for EditorFileDialog. It seems there are several similar icons, but in different colors. Because of this, they handle color differently. As a result, you can see that in light theme darkens red folder (in 4.5 too).

[AdriaandeJongh]

… but now the red folder is brown :P

[Scrawach]

Yep, but it was like this in previous versions too. It's just regression fix. I've also been thinking about fixing this, but it's hard for me to predict what it will affect. And, perhaps, it's supposed to work that way :D

One of the possible solutions. It's required this code changes in themes:

//p_theme->set_icon("folder_thumbnail", "FileDialog", p_theme->get_icon("FolderBigThumb", EditorStringName(EditorIcons)));
p_theme->set_color("folder_icon_color", "FileDialog", (Color(1, 1, 1)).lerp(p_config.accent_color, 0.7));

As result:

But it's required paint Folder.svg (editor\icons\Folder.svg) to white color, because file dock icons use this icons and folder_icon_color together. Yes, it's a bit confusing right now because of the different colors of similar icons.

But it's another issue with that:

[Scrawach]

Another solution would be to multiply folders color by a constant, as it's done in other places. But the red color will still be darker here.

In EditorFileDialog:

Color EditorFileDialog::_get_folder_color(const String &p_path) const {
	Color default_color = FileDialog::_get_folder_color(p_path);
	Color folder_color = FileSystemDock::get_dir_icon_color(p_path, default_color);

	if (!EditorThemeManager::is_dark_icon_and_font() && folder_color != default_color) {
		folder_color *= FileSystemDock::ITEM_COLOR_SCALE;
	}

	return folder_color;
}