As part of the RemoveDIs project, transitioning to non-instruction debug
info, all debug intrinsic handling code needs to be duplicated to handle
DPValues.
--try-experimental-debuginfo-iterators enables the new debug mode in
tests if the CMake option has been enabled.
`getInsertPtAfterFramePtr` now returns an iterator so we don't lose
debug-info-communicating bits.
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Depends on #73500, #74090, #74091.
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