Loading saving cache improvements

[qarmin]

Fixes #1064

• Remove unneeded code duplication in all modules
• more debug info when using RUST_LOG=debug that can help find what works bad/slow
• multithreading removing non existent files
• due using BTreeMap instead HashMap performance may be a little slower, but other changes should give bigger performance gain than that

Since this commit, old cache will not be usable and will probably throw segmentation fault(maybe in future bincode 2 will better handle cache version mismatch)

On i7 4770 and cheap ssd 1GB drive - 114988 results - 17.1 MB size

• loading cache - 300ms
• loading cache with removing outdated files - 370ms
• saving cache - 800ms