DenseSet, SmallPtrSet, SmallSet, SetVector, and StringSet recently
gained C++23-style insert_range.  This patch uses insert_range with
iterator ranges.  For each case, I've verified that foos is defined as
make_range(foo_begin(), foo_end()) or in a similar manner.

DenseSet, SmallPtrSet, SmallSet, SetVector, and StringSet recently
gained C++23-style insert_range.  This patch replaces:

  Dest.insert(Src.begin(), Src.end());

with:

  Dest.insert_range(Src);

This patch does not touch custom begin like succ_begin for now.

Parameter PossiblyLoopIndependent has lost its intended purpose. This
flag is always set to true in all cases when depends() is called, hence
we want to reconsider the utility of this variable and remove it from
the function signature entirely. This is an NFC patch.

To finalise the "RemoveDIs" work removing debug intrinsics, we're
updating call sites that insert instructions to use iterators instead.
This set of changes are those where it's not immediately obvious that
just calling getIterator to fetch an iterator is correct, and one or two
places where more than one line needs to change.

Overall the same rule holds though: iterators generated for the start of
a block such as getFirstNonPHIIt need to be passed into insert/move
methods without being unwrapped/rewrapped, everything else can use
getIterator.

Add an extra know to UnrollingPreferences to let backends control the
maximum budget for SCEV expansions.

This gives backends more fine-grained control on the cost of the runtime
checks for runtime unrolling.

PR: https://github.com/llvm/llvm-project/pull/118316

I'd reverted this in 6c7805d5d1 after a bad stage. Original commit
messsage follows:

[NFC][RemoveDIs] Bulk update utilities to insert with iterators

As part of the RemoveDIs project we need LLVM to insert instructions using
iterators wherever possible, so that the iterators can carry a bit of
debug-info. This commit implements some of that by updating the contents of
llvm/lib/Transforms/Utils to always use iterator-versions of instruction
constructors.

There are two general flavours of update:
 * Almost all call-sites just call getIterator on an instruction
 * Several make use of an existing iterator (scenarios where the code is
   actually significant for debug-info)
The underlying logic is that any call to getFirstInsertionPt or similar
APIs that identify the start of a block need to have that iterator passed
directly to the insertion function, without being converted to a bare
Instruction pointer along the way.

I've also switched DemotePHIToStack to take an optional iterator: it needs
to take an iterator, and having a no-insert-location behaviour appears to
be important. The constructors for ICmpInst and FCmpInst have been updated
too. They're the only instructions that take block _references_ rather than
pointers for certain calls, and a future patch is going to make use of
default-null block insertion locations.

All of this should be NFC.

This reverts commit 3fda50d3915b2163a54a37b602be7783a89dd808.

Apparently I've missed a hunk while staging this; will back out for now.

Picked up here: https://lab.llvm.org/buildbot/#/builders/139/builds/60429/steps/6/logs/stdio