[TON Block Validation] Optimize boc check

[AntonGrishin]

Hello, it`s a PR for https://contest.com/docs/BlockValidationChallenge

I used VTune and look for some Hotspots - test cases, that your provided, show that code is already pretty optimized in single thread execution.
But I found out one - CellStorageStat is looking for hashes in "seen" map (O(logn)) and doesn't use sorted property. So I changed it to unordered_map (O(1) lookup) and gain 10% time for validation-contest-tests set

Unfortunately (for me), I find out this challenge just today, so i had only one evening to work on the task.
P.s: I totally understand, that its not much - but its honest work, so I'm not sure, that this is a complete solution that meets the task.
P.s.2 Also i found that Intel changed the COMPILER ID and now its IntelLLVM, so i changed a CMakeLists.txt.
P.s.3 Not sure that I create the PR in right place, since it`s not clear -_-

BR, Anton