Follow up on 528b13d ([SCEVExp] Add helper to clean up dead instructions
after expansion.) to hoist the SCEVExapnder::eraseDeadInstructions call
from LoopVectorize into the LoopUtils APIs add[Diff]RuntimeChecks, so
that other callers (LoopDistribute and LoopVersioning) can benefit from
the patch.

Split out logic to get noalias/alias_scope metadata to separate function
in LoopVersioning. This will be used to migrate away from
annotateInstWithNoAlias in LV.

Loop Optimizations expect the input loop to be in LCSSA form. But it
seems that LoopVersioning doesn't have any check to see if the loop is
actually in LCSSA form. As a result, if we give it a loop which is not
in LCSSA form but still correct semantically, the resulting
transformation fails to pass through verifier pass with the following
error.

Instruction does not dominate all uses!
%inc = add nsw i16 undef, 1
store i16 %inc, ptr @c, align 1

As the loop is not in LCSSA form, LoopVersioning's transformations leads
to invalid IR! As some instructions do not dominate all their uses.

This patch checks if a loop is in LCSSA form, if not it will call
formLCSSARecursively on the loop before passing it to LoopVersioning.

Fixes: #36998 

Use the more aggressive invalidation method in a number of places
that add incoming values to lcssa phi nodes. It is likely that
it's possible to construct cases with incorrect SCEV preservation
similar to https://github.com/llvm/llvm-project/issues/109333 for
these.

This is a helper to avoid writing `getModule()->getDataLayout()`. I
regularly try to use this method only to remember it doesn't exist...

`getModule()->getDataLayout()` is also a common (the most common?)
reason why code has to include the Module.h header.

Continuing the patch series to get rid of debug intrinsics [0], instruction
insertion needs to be done with iterators rather than instruction pointers,
so that we can communicate information in the iterator class. This patch
adds an iterator-taking insertBefore method and converts various call sites
to take iterators. These are all sites where such debug-info needs to be
preserved so that a stage2 clang can be built identically; it's likely that
many more will need to be changed in the future.

At this stage, this is just changing the spelling of a few operations,
which will eventually become signifiant once the debug-info bearing
iterator is used.

[0] https://discourse.llvm.org/t/rfc-instruction-api-changes-needed-to-eliminate-debug-intrinsics-from-ir/68939

Differential Revision: https://reviews.llvm.org/D152537

Mostly removing includes of InitializePasses.h and Pass.h in
passes that no longer has support for the legacy PM.

Following recent changes to remove non-core features of the legacy PM/optimization pipeline.