Refactor CMake and Dockerfile

[ashvardanian]

Current CMakeLists.txt contains too much boilerplate on relies on external package managers to fetch RocksDB, LevelDB, and WiredTiger. For most of those, we have already tested a much cleaner FetchContent_Declare way, already integrated into UKV.

The same applies to Dockerfile, it has to be entirely rewritten to match the design in UKV.