[8.9] [Fleet] Change default batch size (#161249) (#161260)

# Backport

This will backport the following commits from `main` to `8.9`:
- [[Fleet] Change default batch size
(#161249)](#161249)

<!--- Backport version: 8.9.7 -->

### Questions ?
Please refer to the [Backport tool
documentation](https://github.com/sqren/backport)

<!--BACKPORT [{"author":{"name":"Nicolas
Chaulet","email":"[email protected]"},"sourceCommit":{"committedDate":"2023-07-05T13:49:38Z","message":"[Fleet]
Change default batch size
(#161249)","sha":"8ef128701757ad24617e0c97ab8e0a186bc87ec2","branchLabelMapping":{"^v8.10.0$":"main","^v(\\d+).(\\d+).\\d+$":"$1.$2"}},"sourcePullRequest":{"labels":["release_note:skip","Team:Fleet","v8.9.0","v8.10.0"],"number":161249,"url":"https://github.com/elastic/kibana/pull/161249","mergeCommit":{"message":"[Fleet]
Change default batch size
(#161249)","sha":"8ef128701757ad24617e0c97ab8e0a186bc87ec2"}},"sourceBranch":"main","suggestedTargetBranches":["8.9"],"targetPullRequestStates":[{"branch":"8.9","label":"v8.9.0","labelRegex":"^v(\\d+).(\\d+).\\d+$","isSourceBranch":false,"state":"NOT_CREATED"},{"branch":"main","label":"v8.10.0","labelRegex":"^v8.10.0$","isSourceBranch":true,"state":"MERGED","url":"https://github.com/elastic/kibana/pull/161249","number":161249,"mergeCommit":{"message":"[Fleet]
Change default batch size
(#161249)","sha":"8ef128701757ad24617e0c97ab8e0a186bc87ec2"}}]}]
BACKPORT-->

Co-authored-by: Nicolas Chaulet <[email protected]>

x-pack/plugins/fleet/public/applications/fleet/sections/agents/agent_list_page/index.tsx

@@ -410,6 +410,7 @@ export const AgentListPage: React.FunctionComponent<{}> = () => {
   };
 
   const isCurrentRequestIncremented = currentRequestRef?.current === 1;
+
   return (
     <>
       {isAgentActivityFlyoutOpen ? (
@@ -519,6 +520,17 @@ export const AgentListPage: React.FunctionComponent<{}> = () => {
           <EuiSpacer size="l" />
         </>
       )}
+      {/* TODO serverless agent soft limit */}
+      {showUnhealthyCallout && (
+        <>
+          {cloud?.deploymentUrl ? (
+            <FleetServerCloudUnhealthyCallout deploymentUrl={cloud.deploymentUrl} />
+          ) : (
+            <FleetServerOnPremUnhealthyCallout onClickAddFleetServer={onClickAddFleetServer} />
+          )}
+          <EuiSpacer size="l" />
+        </>
+      )}
       {/* Search and filter bar */}
       <SearchAndFilterBar
         agentPolicies={agentPolicies}

x-pack/plugins/fleet/server/services/setup/upgrade_agent_policy_schema_version.ts

@@ -14,7 +14,7 @@ import {
 import { agentPolicyService } from '../agent_policy';
 import { appContextService } from '../app_context';
 
-const DEFAULT_BATCH_SIZE = 100;
+const DEFAULT_BATCH_SIZE = 2;
 function getOutdatedAgentPoliciesBatch(soClient: SavedObjectsClientContract, batchSize: number) {
   return agentPolicyService.list(soClient, {
     perPage: batchSize,