Use controller revision to manage rolling updates

[liurupeng]

What would you like to be added:
Use controller revision to store the leader/worker template; Support restarting the not updated replicas during rolling update

Why is this needed:

Completion requirements:

This enhancement requires the following artifacts:

• Design doc
• API change
• Docs update

The artifacts should be linked in subsequent comments.

[liurupeng]

/assign

[liurupeng]

same as #238

[ahg-g]

Using controller revision will allow us to avoid using template hashes to detect changes. Using template hashes to detect updates is not reliable across lws controller upgrades.

This will address:

• Replicas restart during rolling upgrade will not use the original worker pod spec #238
• When rollout new controller version, it should not trigger a rolling update #240
• When upgrading to a new LWS version, rolling update gets triggered #281

[ahg-g]

/assign @Edwinhr716