[alloc] Reimplement ghost_tree avl operations iteratively instead of recurisively (Rust)

[williamwutq]

Reimplementing AVL operations in GhostTreeBStackAllocator iteratively

Description: Reimplementing AVL operations in GhostTreeBStackAllocator iteratively instead of recursively to minimize stack usage and provide better opportunity for lock-free, atomic, and thread-safe optimizations under the atomic feature flag in future prs. The implementation should behave identical to the recursive implementation.

Important Feature: No
Type: Allocator - Reimplementation
Magic Number: ALGT
Bulk: No
Tests: Included
Feature Flags: alloc + set
Breaking change: No
New Types: None
Rust Only: No
Fuzz: Yes
Safety Review: Needed: Crash Safety, Invariants

[Copilot]

Pull request overview

This PR reimplements key AVL tree operations used by the GhostTree allocator to be iterative rather than recursive, aiming to reduce recursion-driven stack usage and better support future atomic/thread-safe work while preserving behavior.

Changes:

• Reworked GhostTree AVL insert and best-fit remove to record traversal paths and rebalance iteratively.
• Added an iterative “remove-min” helper to support two-child removals without recursion.
• Converted inorder walk and balanced-tree rebuild steps to iterative stack/ops-driven implementations (Rust and C).

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
src/alloc/ghost_tree.rs	Replaces recursive AVL traversal/rebalance logic with iterative path recording; updates inorder walk and rebuild to iterative forms.
c/bstack_alloc.c	Mirrors the iterative AVL insert/best-fit/remove-min/inorder-walk/build logic in the C implementation.

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[williamwutq]

LGTM