[llvm] [TailDuplicator] Add a limit on the size of predecessors (PR #78582)

[Arthur Eubanks via llvm-commits]

aeubanks wrote:

do we actually know why the previous patch caused things to blow up in this pass? i.e. where the memory usage spike actually happened? was it just that we were doing too much tail duplication after the other change produced code that tended to be tail duplicated? or is there an underlying algorithmic problem that we can fix?

https://github.com/llvm/llvm-project/pull/78582