Fix AnimationPlayer blend_times sorting

[JacobMillner]

Fixes #76491

The current operator< for BlendKeys compares to/from pointers resulting in nondeterministic behavior. You can see this represented in the .tscn file of anything with lots of blend_times resulting in file changes which leads to extra noise in your git commits.

This PR usesStringName::AlphaCompare when making to/from comparisons in order preform a lexicographic order sort rather than one determined by memory location.

[JacobMillner]

tested and working locally with StringName::AlphaCompare 👍

[TokageItLab]

Please squash the commits to follow PR workflow https://docs.godotengine.org/en/stable/contributing/workflow/pr_workflow.html#the-interactive-rebase

[akien-mga]

Thanks! And congrats for your first merged Godot contribution 🎉

[JacobMillner]

Thanks everyone!