Move disjoint flag tracking to OverflowTracking. This enables preserving
disjoint flags in Reassociate.

Depends on https://github.com/llvm/llvm-project/pull/140404

PR: https://github.com/llvm/llvm-project/pull/140406

This has the side effect of fixing the FIXME for when
use-constant-int-for-fixed-length-splat becomes the default.

When ranking operands for an expression tree the reassociate pass also
perform canonicalization, putting constants on the right hand side. Such
transforms was however not registered as modifying the IR. So at the end
of the pass, if not having made any other changes, the pass returned
that all analyses should be kept.

With this patch we make sure to set MadeChange to true when modifying
the IR via canonicalizeOperands. This is to make sure analyses such as
DemandedBits are properly invalidated when instructions are modified.

As part of reassociating add instructions, we may factorize some of the
adds and produce a mul instruction; this patch propagates the source
location of the reassociated tree of instructions to the new mul.

Found using https://github.com/llvm/llvm-project/pull/107279.

As part of RemoveFactorFromExpression, we attempt to remove a factor
from a mul/fmul expression; this may involve generating new
instructions, e.g. to negate the result if the factor was negative in
the original expression. When this happens, the new instructions should
have a DebugLoc set from the instruction that the factored expression is
being used to compute.

Found using https://github.com/llvm/llvm-project/pull/107279.

Currently in Reassociate we may create a set of new instructions when
optimizing an `add`, but we do not set DebugLocs on the new
instructions; this patch propagates the add's DebugLoc to the new
instructions.

Found using #107279.

These date back to when the non-intrinsic format of variable locations
was still being tested and was behind a compile-time flag, so not all
builds / bots would correctly run them. The solution at the time, to get
at least some test coverage, was to have tests opt-in to non-intrinsic
debug-info if it was built into LLVM.

Nowadays, non-intrinsic format is the default and has been on for more
than a year, there's no need for this flag to exist.

(I've downgraded the flag from "try" to explicitly requesting
non-intrinsic format in some places, so that we can deal with tests that
are explicitly about non-intrinsic format in their own commit).

Extends what we already do for i1 types and don't serialize vXi1 logical expressions to improve ILP.

llvm-test-suite numbers
https://github.com/llvm/llvm-project/issues/64840#issuecomment-2053621740
indicate that both reassociations are a net win.

Fixes #64840
Fixes #63946

This PR removes tests with `br i1 undef` under
`llvm/tests/Transforms/ObjCARC, Reassociate, SCCP, SLPVectorizer...`.
After this PR, I'll continue to fix tests under `llvm/tests/CodeGen`,
which has more UB tests than `llvm/tests/Transforms`.