Optionally allow DB to know expected number of blocks at batch transaction start

This will assist in a DB resize check.

src/blockchain_db/berkeleydb/db_bdb.cpp

@@ -1595,7 +1595,7 @@ bool BlockchainBDB::has_key_image(const crypto::key_image& img) const
 // Ostensibly BerkeleyDB has batch transaction support built-in,
 // so the following few functions will be NOP.
 
-void BlockchainBDB::batch_start()
+void BlockchainBDB::batch_start(uint64_t batch_num_blocks)
 {
   LOG_PRINT_L3("BlockchainBDB::" << __func__);
 }

src/blockchain_db/berkeleydb/db_bdb.h

@@ -191,7 +191,7 @@ public:
                             );
 
   virtual void set_batch_transactions(bool batch_transactions);
-  virtual void batch_start();
+  virtual void batch_start(uint64_t batch_num_blocks=0);
   virtual void batch_commit();
   virtual void batch_stop();
   virtual void batch_abort();

src/blockchain_db/blockchain_db.h

@@ -357,7 +357,7 @@ public:
   // release db lock
   virtual void unlock() = 0;
 
-  virtual void batch_start() = 0;
+  virtual void batch_start(uint64_t batch_num_blocks=0) = 0;
   virtual void batch_stop() = 0;
   virtual void set_batch_transactions(bool) = 0;
 

src/blockchain_db/lmdb/db_lmdb.cpp

@@ -1820,7 +1820,7 @@ bool BlockchainLMDB::has_key_image(const crypto::key_image& img) const
   return false;
 }
 
-void BlockchainLMDB::batch_start()
+void BlockchainLMDB::batch_start(uint64_t batch_num_blocks)
 {
   LOG_PRINT_L3("BlockchainLMDB::" << __func__);
   if (! m_batch_transactions)

src/blockchain_db/lmdb/db_lmdb.h

@@ -191,7 +191,7 @@ public:
                             );
 
   virtual void set_batch_transactions(bool batch_transactions);
-  virtual void batch_start();
+  virtual void batch_start(uint64_t batch_num_blocks=0);
   virtual void batch_commit();
   virtual void batch_stop();
   virtual void batch_abort();

src/blockchain_utilities/fake_core.h

@@ -96,9 +96,9 @@ struct fake_core_lmdb
     return m_storage.get_db().add_block(blk, block_size, cumulative_difficulty, coins_generated, txs);
   }
 
-  void batch_start()
+  void batch_start(uint64_t batch_num_blocks = 0)
   {
-    m_storage.get_db().batch_start();
+    m_storage.get_db().batch_start(batch_num_blocks);
   }
 
   void batch_stop()
@@ -150,7 +150,7 @@ struct fake_core_memory
     return 2;
   }
 
-  void batch_start()
+  void batch_start(uint64_t batch_num_blocks = 0)
   {
     LOG_PRINT_L0("WARNING: [batch_start] opt_batch set, but this database doesn't support/need transactions - ignoring");
   }