celldb: version 2

- thread safe cache
- parallel commit
- multiple optimizations
- support of key-value merge operations
- improved tests and benchmarks
- in-memory version won't read from key value after start - uses vector in-memory table now
- use rocksdb::WALRecoveryMode::kTolerateCorruptedTailRecords - do not silently ignore errors during recovery

validator-engine/validator-engine.hpp

@@ -218,6 +218,7 @@ class ValidatorEngine : public td::actor::Actor {
   bool celldb_direct_io_ = false;
   bool celldb_preload_all_ = false;
   bool celldb_in_memory_ = false;
+  bool celldb_v2_ = false;
   td::optional<double> catchain_max_block_delay_, catchain_max_block_delay_slow_;
   bool read_config_ = false;
   bool started_keyring_ = false;
@@ -311,6 +312,9 @@ class ValidatorEngine : public td::actor::Actor {
   void set_celldb_in_memory(bool value) {
     celldb_in_memory_ = value;
   }
+  void set_celldb_v2(bool value) {
+    celldb_v2_ = value;
+  }
   void set_catchain_max_block_delay(double value) {
     catchain_max_block_delay_ = value;
   }