[BasicBlockUtils] SplitLandingPadPredecessors() breaks LoopInfo

SplitLandingPadPredecessors() results in an irreducible loop and makes LoopInfo invalid. Verification results in a crash with the following error:

Assertion `CB != OutsideLoopPreds[i] && "Loop has multiple entry points!"' failed.

Here is the reproduction test where the bad loop has 2 blocks: catch_dest.split-lp ,catch_dest

Before:
```
declare void @foo()

define void @split-lp-predecessors-test() personality ptr null {
entry:
invoke void @foo()
to label %loop unwind label %catch_dest

loop:
invoke void @foo()
to label %latch unwind label %catch_dest

latch:
br label %loop

catch_dest:
%lp = landingpad i32
cleanup
invoke void @foo()
to label %exit unwind label %catch_dest

exit:
ret void
}
```

After SplitBlockPredecessors(catch_dest, { loop }, "", DT, LI):
```
declare void @foo()

define void @split-lp-predecessors-test() personality ptr null {
entry:
invoke void @foo()
to label %loop unwind label %catch_dest.split-lp

loop: ; preds = %latch, %entry
invoke void @foo()
to label %latch unwind label %catch_dest1

latch: ; preds = %loop
br label %loop

catch_dest1: ; preds = %loop
%lpad = landingpad i32
cleanup
br label %catch_dest

catch_dest.split-lp: ; preds = %entry, %catch_dest
%lpad.split-lp = landingpad i32
cleanup
br label %catch_dest

catch_dest: ; preds = %catch_dest.split-lp, %catch_dest1
invoke void @foo()
to label %exit unwind label %catch_dest.split-lp

exit: ; preds = %catch_dest
ret void
}
```