[LiveIntervals] Split live intervals on any dead def

Each dead def of the same virtual register is required to be split into multiple
virtual registers with separate live intervals to avoid MachineVerifier error.

Partially fixes https://github.com/llvm/llvm-project/issues/56050 and
https://github.com/llvm/llvm-project/issues/56051

Reviewed By: qcolombet

Differential Revision: https://reviews.llvm.org/D130477