Fix Memory64Lowering table.copy size wrapping for mixed tables

[sumleo]

Summary

visitTableCopy wrapped curr->size using only the dest table's type, but the wasm spec (and child-typer.h) defines the size type as i64 only when both source and dest tables are 64-bit. When copying between a 64-bit and a 32-bit table, the size is i32, but wrapping checks only the dest table — causing an assertion failure (assert(ptr->type == Type::i64)) when dest is 64-bit but source is 32-bit.

Fix: Check both tables before wrapping the size operand, matching the type logic in child-typer.h.

Split from #8311 per review feedback.

Test plan

• New lit test memory64-lowering-table-copy.wast covering:
  • Copy from 64-bit to 32-bit table (size stays i32, no crash)
  • Copy from 32-bit to 64-bit table (size stays i32, no crash)
  • Copy between two 64-bit tables (all operands including size are wrapped)
• All 309 unit tests pass