[release-3.5] Add e2e test to verify etcd is able to automatically fix the issue

[ahrtr]

caused by #19557

Please read https://github.com/etcd-io/etcd/blob/main/CONTRIBUTING.md#contribution-flow.

[ahrtr]

Link to

• [release-3.5] Learner promotion isn't persisted to v3store (bbolt) #19557
• [release-3.5] [Solution 2] Auto sync members in v3store if Islearner is the only field that differs between v2store and v3store #19606

[fuweid]

LGTM

[k8s-ci-robot]

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[fuweid]

ping @serathius @siyuanfoundation

We don't need further code change. ETCD server always publishes member's attributes during starting. This update is updated through RAFT. In v3.5 release, member information is from v2 store, which is always valid and correctness. For the UpdateAttributes, it gets member info from v2 store data, updates attributes and then applies it into backend. Since this raft log index is higher than applied in v3 backend, so UpdateAttributes always applies change into v3 backend.

etcd/server/etcdserver/api/membership/cluster.go

Lines 491 to 503 in 3c65dfa

	func (c *RaftCluster) UpdateAttributes(id types.ID, attr Attributes, shouldApplyV3 ShouldApplyV3) {
	c.Lock()
	defer c.Unlock()
	if m, ok := c.members[id]; ok {
	m.Attributes = attr
	if c.v2store != nil {
	mustUpdateMemberAttrInStore(c.lg, c.v2store, m)
	}
	if c.be != nil && shouldApplyV3 {
	unsafeSaveMemberToBackend(c.lg, c.be, m)
	}
	return

Since we already allows ETCD to override existing member information, this publish call will help us do migration. So we don't need code change. Just add e2e test to ensure that.

[siyuanfoundation]

/lgtm

[ahrtr]

@ivanvc we are ready to release 3.5.20