Revert "Do not ever collapse two intrinsics with the iscast attribute"

This reverts commit a281a0ddaf104658349c57bee1b4c2838ae04f7e.
Revert "Stop GVN from collapsing cast intrinsics"

This reverts commit 4c3a230ec8d5bf586a989e3116850b1485f3466b.
Replace the IsCast attribute with TypedIntrinsic
Fix parsing of duetto attributes