This patch trivially extends support for DbgValueInst recovery to
DPValues in LoopStrengthReduce; they are handled identically, so this is
mostly done by reusing the DbgValueInst code (using templates or
auto-parameter lambdas to reduce actual code duplication).
When transforming a loop terminating condition into a "max" comparison,
the DebugLoc from the old condition should be set on the newly created
comparison. They are the same operation, just optimized. Fixes PR48067.
Differential Revision: https://reviews.llvm.org/D98218