Fix NULL dereference on allocation failure and validate invalid JSON Patch move operations

[priyansx2233]

Summary

This PR fixes two critical issues in cJSON_Utils.c:

1. Prevents NULL pointer dereferences when cJSON_malloc() fails in multiple public API code paths.
2. Adds RFC 6902-compliant validation to reject move operations that attempt to move a value into one of its own descendants before any document mutation occurs.

Changes

1. Handle allocation failures safely

Added missing NULL checks after calls to cJSON_malloc() in the following functions:

• compose_patch()
• create_patches()
• cJSONUtils_FindPointerFromObjectTo()

On allocation failure, the functions now:

• Return an appropriate error instead of dereferencing a NULL pointer.
• Free any previously allocated resources before returning to avoid memory leaks.

2. Enforce RFC 6902 move validation

Added validation for JSON Patch move operations to ensure the destination path is not the source path or one of its descendants, as required by RFC 6902 §4.4.

The validation is performed before detach_path() is called, preventing partial document modification when an invalid move operation is supplied.

Benefits

• Prevents crashes caused by out-of-memory conditions or custom allocators returning NULL.
• Eliminates a memory leak on allocation failure in cJSONUtils_FindPointerFromObjectTo().
• Ensures JSON Patch move operations comply with RFC 6902.
• Prevents unintended document mutation when invalid move operations are processed.

Testing

• Verified that all modified allocation paths return gracefully when cJSON_malloc() fails.
• Added regression tests covering allocation failure handling.
• Added tests for invalid move operations where the destination is a descendant of the source, ensuring the patch is rejected and the original document remains unchanged.
• Ran the existing test suite to confirm no regressions.