[Uniformity] Legacy PM: Set UniformityInfoWrapperPass isCFGOnly to false (#148165)

Currently, Uniformity Analysis is preserved in the Legacy PM when a pass
sets `setPreservesCFG()`. This is incorrect: any values' uniformity not
only depends on the CFG, but also on the uniformity of other values, so
a CFG-preserving change in many cases doesn't preserve uniformity
analysis.

This corrected behavior also matches the behavior of the new PM.

---

On its own, this change does not affect the pass pipeline because of the
happenstance of pass ordering. I also created a PR to change
AMDGPULateCodeGenPrepare (#148167), this will have an actual impact on
pass executions. That PR also includes changes to the
`amdgpu/llc-pipeline.ll` test in order to check that this change works,
but if this is preferred, I would also be happy to try to extend this PR
to add an isolated test case; though my personal opinion is that the
test in #148167 should suffice, as it should also accurately pinpoint
failures related to this change.

---

I ran `git-clang-format` on my changes. I tested them using the
`check-llvm` target; no unexpected failures occurred.

Author: J-MR-T

llvm/lib/Analysis/UniformityAnalysis.cpp

@@ -146,12 +146,12 @@ char UniformityInfoWrapperPass::ID = 0;
 UniformityInfoWrapperPass::UniformityInfoWrapperPass() : FunctionPass(ID) {}
 
 INITIALIZE_PASS_BEGIN(UniformityInfoWrapperPass, "uniformity",
-                      "Uniformity Analysis", true, true)
+                      "Uniformity Analysis", false, true)
 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
 INITIALIZE_PASS_DEPENDENCY(CycleInfoWrapperPass)
 INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)
 INITIALIZE_PASS_END(UniformityInfoWrapperPass, "uniformity",
-                    "Uniformity Analysis", true, true)
+                    "Uniformity Analysis", false, true)
 
 void UniformityInfoWrapperPass::getAnalysisUsage(AnalysisUsage &AU) const {
   AU.setPreservesAll();