We can use *Set::insert_range to replace "for" loop-based insertions.
In some cases, we can further fold insert_range into the set
declaration.

We can use *Set::insert_range to collapse:

  for (auto Elem : Range)
    Set.insert(E);

down to:

  Set.insert_range(Range);

In some cases, we can further fold that into the set declaration.

`llvm::Type::getPointerTo()` is to be deprecated.
Replace remaining uses of it.

If modified attribute list is invalid, reverting the change is a
low-cost maintainence solution as compared to examples like
[this](https://github.com/llvm/llvm-project/blob/main/llvm/tools/bugpoint/CrashDebugger.cpp#L368).
This will ensure that the ListReducer maintains the sanctity of any
new attribute dependencies added in the future/already present.

Reviewed By: modocache

Differential Revision: https://reviews.llvm.org/D154348

Differential Revision: https://reviews.llvm.org/D138617

Replacing the following instances of UndefValue with PoisonValue, where the UndefValue is used as an arbitrary value:

- llvm/lib/CodeGen/WinEHPrepare.cpp
`demotePHIsOnFunclets`: RAUW arbitrary value for lingering uses of removed PHI nodes

 - llvm/lib/Transforms/Utils/BasicBlockUtils.cpp
`FoldSingleEntryPHINodes`: Removes a self-referential single entry phi node.

 - llvm/lib/Transforms/Utils/CallGraphUpdater.cpp
`finalize`: Remove all references to removed functions.

- llvm/lib/Transforms/Utils/ScalarEvolutionExpander.cpp
`cleanup`: the result is not used then the inserted instructions are removed.

 - llvm/tools/bugpoint/CrashDebugger.cpp
`TestInts`:  the program is cloned and instructions are removed to narrow down source of crash.

Differential Revision: https://reviews.llvm.org/D133640

Identified with readability-qualified-auto.