No minimum block time in Runtime

[JoshOrndorff]

What does it do?

This PR removes the requirement from the runtime that blocks be at least 3 seconds apart. With that requirement gone, we are free to remove the mock timestamp provider.

Solves https://purestake.atlassian.net/browse/MOON-318 (@albertov19)

What important points reviewers should know?

The mock timestamp was introduced because our use of Aura in the standalone node required a minimum time stamp on the order of the block time. Now that the standalone node is removed, there is no reason need to mock the timestamp, or even make arbitrary requirements on a minimum block duration.

Drawback?

One potential drawback of this change is that our runtime logic no longer requires blocks to be any particular amount of time apart anymore. In practice they should always be at least six seconds apart because of the relay chain. And further, correct nodes should ensure that each block's timestamp is withing 30 seconds of its own. Currently the relay chain calidators will not check these timestamps, but this is planned: paritytech/cumulus#343

What value does it bring to the blockchain users?

The block timestamp in will reflect the "real" wall clock time even when running the dev service.

Checklist

• ❌ Does it require a purge of the network?
• ✔️ You bumped the runtime version if there are breaking changes in the runtime ?
• ❌ Does it require changes in documentation/tutorials ?

[crystalin]

We won't merge this into v6, it will be merged for the tutorial-v6 however

[JoshOrndorff]

We won't merge this into v6

Sounds good 👍

it will be merged for the tutorial-v6 however

I don't understand this. Why do we want a separate tutorials tag? That means someone who completes a tutorial, and then wants to sync a node to alphanet will have to re-checkout and rebuild a different node (or pull a different docker image). It also makes it impossible to have a tutorial about running an alphanet node.

Can we just make a new tag v0.6.1 when this goes in and then make the tutorials and the alphanet recommend that version?

[crystalin]

@JoshOrndorff I believe the tutorial tags are not meant to run an alphanet node. They are designed for developers to run it locally.
@albertov19 correct me if I'm wrong

[JoshOrndorff]

the tutorial tags are not meant to run an alphanet node

Yes I understand they aren't to run an alphanet node. But they should run the same version of the software. They just use --dev instead of --chain alphanet.

[tgmichel]

Looks good to me!