core: preallocate batch size in bloomIndexer (ethereum#25289)

This change reduces allocations when committing bloombits indexes
by creating the database batch with a larger initial size.

core/bloom_indexer.go

@@ -75,7 +75,7 @@ func (b *BloomIndexer) Process(ctx context.Context, header *types.Header) error
 // Commit implements core.ChainIndexerBackend, finalizing the bloom section and
 // writing it out into the database.
 func (b *BloomIndexer) Commit() error {
-	batch := b.db.NewBatch()
+	batch := b.db.NewBatchWithSize((int(b.size) / 8) * types.BloomBitLength)
 	for i := 0; i < types.BloomBitLength; i++ {
 		bits, err := b.gen.Bitset(uint(i))
 		if err != nil {