topicsdb search optimization

[rus-alex]

New topicsdb/Index.searchParallel() instead of topicsdb/Index.searchLazy() is optimized for large datadir.
Gets ~4 times faster (39s vs 176s) on mainnet query

curl -X POST 'http://localhost:4000' -H 'Content-Type: application/json' -d '                                                                                                                          
{                                                                                                                                                                                                           
    "jsonrpc": "2.0",                                                                                                                                                                                       
    "method": "eth_getLogs",                                                                                                                                                                                
    "params": [{                                                                                                                                                                                            
"fromBlock": "0x256e898",                                                                                                                                                                                         
"toBlock": "0x2586f37",                                                                                                                                                                                     
"topics": ["0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef", null, "0x00000000000000000000000089716ad7edc3be3b35695789c475f3e7a3deb12a"]                                                
    }],                                                                                                                                                                                                     
    "id": 1                                                                                                                                                                                                 
}'