CodeRegion's were previously passed as Value*, but then immediately
upcast to BasicBlock. Let's keep the type information around until the
use cases for non-BasicBlock code regions actually materialize.

Identified with misc-include-cleaner.

Convert many instances of:
  Fn = Intrinsic::getOrInsertDeclaration(...);
  CreateCall(Fn, ...)
to the equivalent CreateIntrinsic call.

Rename the function to reflect its correct behavior and to be consistent
with `Module::getOrInsertFunction`. This is also in preparation of
adding a new `Intrinsic::getDeclaration` that will have behavior similar
to `Module::getFunction` (i.e, just lookup, no creation).

This used to be necessary to fetch the DataLayout, but isn't anymore.

Similar to https://github.com/llvm/llvm-project/pull/96902, this adds
`getDataLayout()` helpers to Function and GlobalValue, replacing the
current `getParent()->getDataLayout()` pattern.

Reverts the above commit, as it updates a common header function and
did not update all callsites:

  https://lab.llvm.org/buildbot/#/builders/29/builds/382

This reverts commit 6481dc57612671ebe77fe9c34214fba94e1b3b27.

Uses the new InsertPosition class (added in #94226) to simplify some of
the IRBuilder interface, and removes the need to pass a BasicBlock
alongside a BasicBlock::iterator, using the fact that we can now get the
parent basic block from the iterator even if it points to the sentinel.
This patch removes the BasicBlock argument from each constructor or call
to setInsertPoint.

This has no functional effect, but later on as we look to remove the
`Instruction *InsertBefore` argument from instruction-creation
(discussed
[here](https://discourse.llvm.org/t/psa-instruction-constructors-changing-to-iterator-only-insertion/77845)),
this will simplify the process by allowing us to deprecate the
InsertPosition constructor directly and catch all the cases where we use
instructions rather than iterators.

Fixes: https://github.com/llvm/llvm-project/issues/85254

Hardware loops inserts PHIs at the position `getFirstNonPhi()`, which is
incorrect - instead, `getFirstNonPhiIt()` is required to not insert the
PHI after any debug records that immediately follow the last existing
PHI.

This pass was adding new function calls without adding the strictfp
attribute as required by the rules laid out in the langref. With this
change a make check has 4-5 fewer failing tests with the Verifier
changes in D146845.

LangRef:
https://llvm.org/docs/LangRef.html#constrained-floating-point-intrinsics

Test failures found with "https://reviews.llvm.org/D146845".