Testnet and Stagenet chain configurations; Minor bug fixes; Removed unused consensus; Update Go package refs

[andrepatta]

This PR includes the following changes.

Chain config:

• New chain configuration for test network (--testnet) with pre-allocated funds
• New chain configuration for stage network (--stagenet) with pre-allocated funds

Consensus:

• Removed unused standard IBFT consensus
• Renamed and moved modified version of IBFT (QBFT) to consensus/istanbul
• Removed the ability to customize some IBFT settings through startup flags and/or custom genesis
• Make sure we always use Ceil(2N/3) for consensus messages

Binaries:

• Renamed geth to etn-sc
• Renamed ethkey to etnkey
• Properly set version in params/version.go
• Update Dockerfile entrypoint

Default Data Dir:

• Mainnet default root dir changed from ~/.ethereum to ~/.electroneum-sc
• Mainnet default data dir changed from ~/.ethereum/geth to ~/.electroneum-sc/etn-sc
• Stagenet default root dir set to ~/.electroneum-sc/stagenet
• Stagenet default data dir set to ~/.electroneum-sc/stagenet/etn-sc
• Testnet default root dir set to ~/.electroneum-sc/testnet
• Testnet default data dir set to ~/.electroneum-sc/testnet/etn-sc

Fixes:

• Make sure we don't wait 7 blocks to set it as canonical if using IBFT (because of 1BF)
• Fixed an issue where a validator could provide any coinbase address for block rewards
• Make sure we don't use DNS peer-finding for now (needs further setup)
• Updated some missing NetworkId entries that were still using the old value (1 -> 52014)
• Fixed an issue where BootstrapNodes weren't properly set (from config.toml) when running geth with a test network flag (also PR'd to go-ethereum https://github.com/ethereum/go-ethereum/pull/25174#issue-1285398601)

Other:

• Renamed all ethereum/go-ethereum Go package references to electroneum/electroneum-sc