[LVI] Pointer equivalence implied without considering pointer provenance

Similarly to what has already been fixed in GVN, and currently tracked in SCCP (https://github.com/llvm/llvm-project/issues/159565), when assuming a pointer equality, CVP happens to propagate the known constant (or the pointer itself on the inverse condition), without however considering the pointer provenance, which may be different (or non-existent).

```llvm
define ptr @src(ptr %p) {
entry:
%cond = icmp eq ptr %p, inttoptr (i64 -1 to ptr)
br i1 %cond, label %join, label %bb.1

bb.1:
br label %join

join:
%phi = phi ptr [ %p, %entry ], [ inttoptr (i64 -1 to ptr), %bb.1 ]
ret ptr %phi
}

define ptr @tgt(ptr %p) {
%cond = icmp eq ptr %p, inttoptr (i64 -1 to ptr)
br i1 %cond, label %join, label %bb.1

bb.1:
br label %join

join:
ret ptr inttoptr (i64 -1 to ptr)
}
```

Alive2: https://alive2.llvm.org/ce/z/GkRymb.