Improve and simplify mirrornet conversion jobs
- Move gitlab CI inlined code into dedicated bash script files for better maintenance and simplifed local usage
- Allow to define
NUMBER_OF_BLOCKS
as 0, what means to peform block_log conversion into to the end of fresh mainnet block log. Mainnet block log should be incrementally synced from pointed remote ( i.e. https://gtg.openhive.network/get/blockchain/block_log )