1. More fixes to improve download speed of the block snapshot files. Increased chunk size from default 16k to 2m (maximum possible), to reduce number of chunks and improve performance. Upgrade to newer version of anacrolix/torrent library which uses heap on generics (it is faster than without generics).
2. Revert of the skip analysis optimisation fix to fix mainnet sync error at block 13119520. The optimisation will be applied later once this block is added to exclusion list.
3. Improved atomicity in handling snapshot files, which enables correct working of RPC daemon when it is not connected to Erigon or when Erigon is still syncing.
4. Upgrade to MDBX 0.11.7 - no functional changes, simply official release version.
5. Removed the concept of preverified hashes, and other simplifications of header downloader (in attempt to fix the problem of stuck download).