Extract parent proxy handlers and simplify parent-member lookup

[PJacek]

Description of the problem being solved:

JIT traces were aborting due to per-instance dynamic metamethods and anonymous closures created for parent lookups and constructor calls.

Example trace aborts:

[TRACE --- (969/3) ModStore.lua:99 -- NYI: bytecode FNEW   at Common.lua:131]
[TRACE --- CalcPerform.lua:41 -- inner loop in root trace at Common.lua:123]
[TRACE --- (165/2) ModList.lua:87 -- NYI: bytecode FNEW   at Common.lua:131]
[TRACE --- PassiveSpec.lua:1199 -- inner loop in root trace at Common.lua:104]
[TRACE --- PassiveSpec.lua:1121 -- inner loop in root trace at Common.lua:104]
[TRACE --- Common.lua:102 -- inner loop in root trace at Common.lua:104]
[TRACE --- CalcSetup.lua:890 -- inner loop in root trace at Common.lua:104]
[TRACE --- (997/2) ModList.lua:87 -- NYI: bytecode FNEW   at Common.lua:131]
[TRACE --- Common.lua:122 -- NYI: bytecode FNEW   at Common.lua:131]
[TRACE --- (997/2) ModList.lua:87 -- NYI: bytecode FNEW   at Common.lua:131]
[TRACE --- (997/2) ModList.lua:87 -- NYI: bytecode FNEW   at Common.lua:131]

Changes made:

• Extracted reusable local helper functions parentIndex and parentCall.
• Updated proxy metatables to store _parent and _object and reuse the extracted handlers instead of creating new anonymous closures per parent.
• Simplified parent-to-child member resolution to avoid dynamic per-object __index logic.

Impact:

• Behaviour is unchanged for normal usage but members added to a parent after child classes are created will no longer automatically become visible to existing children.
• No more FNEW trace aborts (verified using jit.v). While the exact counts vary between runs due to non-deterministic nature of the JIT, I observed fewer abort and more successful traces in Common.lua.
• Possible slight performance increase. Because of run-to-run variance I’m not presenting hard numbers, but I believe this change is a net positive for interaction with the rest of the codebase.