Revert "[SelectionDAG] Handle more opcodes in canCreateUndefOrPoison (#84921)" and more...

This reverts:
b3c55b70 - "[SelectionDAG] Handle more opcodes in canCreateUndefOrPoison (#84921)"
(because it updates a test case that I don't know how to resolve the conflict for)
8e2f6495 - "[DAGCombiner] Do not always fold FREEZE over BUILD_VECTOR (#85932)"
73472c59 - "[SelectionDAG] Treat CopyFromReg as freezing the value (#85932)"

Due to a test suite failure on AArch64 when compiling for SVE.
https://lab.llvm.org/buildbot/#/builders/197/builds/13955

clang: ../llvm/llvm/include/llvm/CodeGen/ValueTypes.h:307: MVT llvm::EVT::getSimpleVT() const: Assertion `isSimple() && "Expected a SimpleValueType!"' failed.