[WebAssembly] Add more lowerings for wide-arithmetic (#132430) This commit is the result of investigation and discussion on WebAssembly/wide-arithmetic#6 where alternatives to the `i64.add128` instruction were discussed but ultimately deferred to a future proposal. In spite of this though I wanted to apply a few changes to the LLVM backend here with `wide-arithmetic` enabled for a few minor changes: * A lowering for the `ISD::UADDO` node is added which uses `add128` where the upper bits of the two operands are constant zeros and the result of the 128-bit addition is the result of the overflowing addition. * The high bits of a `I64_ADD128` node are now flagged as "known zero" if the upper bits of the inputs are also zero, assisting this `UADDO` lowering to ensure the backend knows that the carry result is a 1-bit result. A few tests were then added to showcase various lowerings for various operations that can be done with wide-arithmetic. They don't all optimize super well at this time but I wanted to add them as a reference here regardless to have them on-hand for future evaluations if necessary.
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