Move some of the key parameters to env vars or config file

[Tofel]

Following hardcoded settings increase Ethereum-based events detection on environments like our devnet to anything between a couple of minutes to 20 minutes, which makes it unfeasable for testing and test automation. Let's move them to env vars or a config file.

Settings in question:

• main_loop.go -> const defaultLoopDur
• orchestrator/eth_event_watcher.go -> const defaultBlocksToSearch