Fix LuaJIT compatibility on dev

[JLawMcGraw]

Description of the problem being solved:

Recent dev changes introduced syntax accepted by Luau but not by the LuaJIT 2.1 runtime used by Path of Building and its test workflow. Attribute-node switching also recursively deep-copies references into the passive-tree graph, which greatly increases allocation and can exhaust LuaJIT table capacity during replay-heavy workloads.

This replaces the incompatible operators, optional chaining, continue statements, and arrow function with LuaJIT-compatible equivalents. It also switches attribute nodes with a shallow structural copy while copying the stat-description array that ReplaceNode mutates.

Steps taken to verify a working solution:

• Parsed all 1,121 Lua files with stock LuaJIT 2.1.
• Ran all 53 system spec files: 824 passed, 0 failed, 2 expected failures, 18 pending.
• Swept all 293 attribute nodes and verified each override while reducing allocation from about 5 MB to about 993 KB.

Link to a build that showcases this PR:

N/A; this is runtime compatibility and passive-tree correctness.

Before screenshot:

N/A

After screenshot:

N/A

[vaisest]

This syntax is part of LuaJIT v2.1 as of July 2026. Update your LuaJIT: LuaJIT/LuaJIT#1476