[SelectionDAGISel] Don't merge input chains if it would put a token factor in the way of a glue. (#167805) In the new test, we're trying to fold a load and a X86ISD::CALL. The call has a CopyToReg glued to it. The load and the call have different input chains so they need to be merged. This results in a TokenFactor that gets put between the CopyToReg and the final CALLm instruction. The DAG scheduler can't handle that. The load here was created by legalization of the extract_element using a stack temporary store and load. A normal IR load would be chained into call sequence by SelectionDAGBuilder. This would usually have the load chained in before the CopyToReg. The store/load created by legalization don't get chained into the rest of the DAG. Fixes #63790
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