Cache StringNames and NodePaths when casting from string in C#

[Joy-less]

I previously discussed this in detail in the Godot Proposals repository: godotengine#10826

The TL;DR is that StringNames and NodePaths create insidious garbage collection performance spikes in C#, due to allocation of new objects inside implicit casts.

Input.IsActionPressed("action"); // Allocated a StringName.
GetNode("path/to/node"); // Allocated a NodePath.

This is my current workaround:

global using static RecycleExtensions;

using ZiggyCreatures.Caching.Fusion;

public static class RecycleExtensions {
    private static readonly FusionCache StringNameCache = new(new FusionCacheOptions());
    private static readonly FusionCache NodePathCache = new(new FusionCacheOptions());

    /// <summary>
    /// Converts the string to a StringName, recycling if possible.
    /// </summary>
    public static StringName StringName(string String) {
        return StringNameCache.GetOrSet(String, _ => (StringName)String);
    }
    /// <summary>
    /// Converts the string to a NodePath, recycling if possible.
    /// </summary>
    public static NodePath NodePath(string String) {
        return NodePathCache.GetOrSet(String, _ => (NodePath)String);
    }
}

StringName MyStringName = StringName("test");
NodePath MyNodePath = NodePath("test");

The solution would be one of the following:

1. Remove StringNames and NodePaths, since they don't add much value.
2. Remove StringNames and NodePaths from the C# API.
3. Put the caching logic from the workaround inside the implicit casts to StringName/NodePath (simplest solution).