[Security Solution] Add Integration bottom bar positioned changed fro…

…m fixed to sticky (elastic#174494)

## Summary

- [x] Fixes a bug where the bottom bar becomes uncentered when the side
navigation panel is open

This bug was most likely caused by this change here:
elastic@0a2148f.
Since this scss rule was added to `fixed` bottom bars only, making the
bottom bar position `sticky` seemed like the best solution that will not
affect other areas of the app. One difference from the fixed position is
that if the window size is bigger than the onboarding directions, the
bottom bar will not be touching the bottom of the viewing window.

## Screenshot

BEFORE

![image](https://github.com/elastic/kibana/assets/56409205/63b6d90f-7905-4e65-9bfd-a982ca2ac871)

![image](https://github.com/elastic/kibana/assets/56409205/9760b5a9-a97f-4e63-a6cb-4c90cbc55470)


AFTER

![image](https://github.com/elastic/kibana/assets/56409205/9fdf89a5-f801-473f-8416-722b7978fcfe)

![image](https://github.com/elastic/kibana/assets/56409205/edf7ce39-f149-4d46-890f-b1f99cf77f43)

Co-authored-by: Kibana Machine <[email protected]>

x-pack/plugins/fleet/public/applications/fleet/sections/agent_policy/create_package_policy_page/multi_page_layout/components/bottom_bar.tsx

@@ -50,7 +50,7 @@ export const CreatePackagePolicyBottomBar: React.FC<{
 }) => {
   const Bar = noAnimation ? NoAnimationCenteredRoundedBottomBar : CenteredRoundedBottomBar;
   return (
-    <Bar>
+    <Bar position="sticky">
       <EuiFlexGroup justifyContent="spaceBetween" alignItems="center">
         <EuiFlexItem grow={false}>
           <EuiFlexItem grow={false}>