Support logging out of projects

[legrego]

The MVP project experience will not include support for Single Log-out ("SLO"). This means that the cloud console and Kibana will maintain independent sessions, which must be independently managed.

Given this constraint, the user avatar menu should not include an explicit "Logout" link, because that gives the false impression that we are terminating their Elastic Session, but we are in fact only invalidating the Kibana session.

After discussing with @bytebilly, @tsullivan, and @sixstringcode, we have decided on the following:

1. For serverless projects, we will replace the existing Logout link with a Close project link.
2. Clicking the Close project link will:
   a) Invalidate the Kibana session (just as our Logout link does today)
   b) Redirect the user to their cloud console, where they can see their project list. This URL can be found via the xpack.cloud.base_url config property, which is already exposed via the cloud.baseUrl property on the cloud plugin's setup contract:

   kibana/x-pack/plugins/cloud/public/plugin.tsx

   Lines 76 to 96 in 02a43a1

   	return {
   	cloudId: id,
   	deploymentId: parseDeploymentIdFromDeploymentUrl(this.config.deployment_url),
   	cname,
   	baseUrl,
   	...this.getCloudUrls(),
   	elasticsearchUrl: decodedId?.elasticsearchUrl,
   	kibanaUrl: decodedId?.kibanaUrl,
   	cloudHost: decodedId?.host,
   	cloudDefaultPort: decodedId?.defaultPort,
   	trialEndDate: trialEndDate ? new Date(trialEndDate) : undefined,
   	isElasticStaffOwned,
   	isCloudEnabled: this.isCloudEnabled,
   	isServerlessEnabled: this.isServerlessEnabled,
   	serverless: {
   	projectId: this.config.serverless?.project_id,
   	},
   	registerCloudService: (contextProvider) => {
   	this.contextProviders.push(contextProvider);
   	},
   	};

[elasticmachine]

Pinging @elastic/kibana-security (Team:Security)

[azasypkin]

Redirect the user to their cloud console, where they can see their project list. This URL can be found via the xpack.cloud.base_url config property, which is already exposed via the cloud.baseUrl property on the cloud plugin's setup contract:

Small correction, we need cloud.baseUrl or the upcoming cloud.projectsUrl on the server-side, but it's currently only exposed on the client side. We're asking to expose this information on the server-side as well in https://github.com/elastic/kibana/pull/163076/files#r1284523872

UPDATE: It has been resolved in #163379