Fix defrag issues for pubsub and lua

[sundb]

This PR fixes two defrag issues.

1. Fix a use-after-free issue caused by updating dictionary keys after a pubsub channel is reallocated.
   This issue was introduced by Implement defragmentation for pubsub kvstore #13058

2. Fix potential use-after-free for lua during AOF loading with defrag
   This issue was introduced by Implement defragmentation for pubsub kvstore #13058
   This fix follows Fix crash during lua script defrag #14319
   This PR updates the LuaScript LRU list before script execution to prevent accessing a potentially invalidated pointer after long-running scripts.

Note that both of these issues were introduced since 7.4, so we can fix them together.

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[Copilot]

Pull Request Overview

This PR fixes defragmentation issues for pubsub and lua functionality that were introduced by a previous change. The fix addresses problems where memory defragmentation could reallocate objects that were still being referenced, leading to potential use-after-free scenarios.

• Moved lua script execution to occur after LRU list manipulation to prevent accessing reallocated memory
• Added a new dictionary lookup function that uses pointer comparison instead of key comparison for defrag scenarios
• Updated pubsub defrag callback to use the new lookup method to handle reallocated channel names

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
src/eval.c	Reordered lua script execution and LRU operations, added safety comment about memory reallocation
src/dict.h	Added declaration for new dictFindByHashAndPtr function
src/dict.c	Implemented dictFindByHashAndPtr function for pointer-based dictionary lookups
src/defrag.c	Updated pubsub defrag callback to use hash and pointer lookup instead of key-based lookup

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