[llvm] [DomTreeConstr][NFC] Resize NodeInfos once on construction (PR #211998)

[Alexis Engelke via llvm-commits]

aengelke wrote:

Minor perf improvement: https://llvm-compile-time-tracker.com/compare.php?from=3a7ac5aacc415bc954cbb84b558371a61a013659&to=98e24ca7afca21a41e16482f5cfc08db50795cff&stat=instructions:u

https://github.com/llvm/llvm-project/pull/211998