Reduce ZetaChain Blocktime

[CharlieMc0]

We want to reduce the ZetaChain blocktime down to 2 or 3 seconds. This will make it easier for developer and users to submit data on-chain and reduces the wait time after submitting a transaction. It also makes are more competitive with other L1s when comparing specs side to side.

Describe the solution you'd like
Ultimately we want 3 seconds or faster block times. I think 2 seconds is achievable with minimal changes.

[CharlieMc0]

These are the subtasks I know about but there are probably more I am not thinking of.

• Remove any hardcoded references to the 6 second block time
• Ensure emissions calculations are updated
• Force all nodes to update their timeout_commit and other values in config.toml at upgrade time.

[swift1337]

I think this one (#350) is a blocker as well...