add sharding feature for ClusterSynchroManager

[jxustc]

What type of PR is this?
/kind feature

What this PR does / why we need it:
Implement the basic sharding feature of the ClusterSynchroManager

Which issue(s) this PR fixes:
Fixes #599

Special notes for your reviewer:
This is a PR for the V1.0 version of the ClusterSynchroManager sharding feature, based on the latest design version discussed previously
Does this PR introduce a user-facing change?:

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[Iceber]

Rearranged the logic（pseudocode）：

func reconcileCluster (){
   // To ensure coherent logic, we can add prejudgements in reconcileCluster
    if status.sharding == nil && spec.sharding != name{
        return
    }

    if status.sharding != nil && status.sharding != name {
        return
    }

    // The cluster will be in the following state：
    // spec.sharding == name and (status.sharding ==nil or status.sharding == name)
    // spec.sharding != name and status != nil and status.sharding == name


    if delele {
        do_delete....
        return
    }

    if spec.sharding != name {
        unmanage_and_set_nil()
        return
    }

    set_sharding_name()
    ...
}

It might be useful.

[jxustc]

Rearranged the logic（pseudocode）：

func reconcileCluster (){
   // To ensure coherent logic, we can add prejudgements in reconcileCluster
    if status.sharding == nil && spec.sharding != name{
        return
    }

    if status.sharding != nil && status.sharding != name {
        return
    }

    // The cluster will be in the following state：
    // spec.sharding == name and (status.sharding ==nil or status.sharding == name)
    // spec.sharding != name and status != nil and status.sharding == name


    if delele {
        do_delete....
        return
    }

    if spec.sharding != name {
        unmanage_and_set_nil()
        return
    }

    set_sharding_name()
    ...
}

It might be useful.

Thanks for the suggestion, I will improve it over the weekend

[Iceber]

Others look good, only a little bit of modification needed

[Iceber]

I think this could be put into a separate function, which would add more comprehensive unit testing to it.
But it can be optimized in a new pr.

[calvin0327]

Do we need to check whether the resource already exists here?

[Iceber]

The leaderelection will take care of checking for the resource, and if it already exists then it will race for it.

[Iceber]

LGTM, Thanks