[Guided Onboarding] Use new images for landing page (#147443)

Replacing the landing page with new images, addresses [issue
#147384](https://github.com/elastic/kibana/issues/147384)

<img width="1710" alt="image"
src="https://user-images.githubusercontent.com/11224465/207354781-70600f14-1187-4d10-ab65-3fd7e380fe4a.png">

@yuliacech @alisonelizabeth : a couple of notes:
- I was given both SVG and PNGs, in this task I just replaced the old
PNGS with the new ones, do you think I should use SVGs instead - or does
not really matter?
- The branding team made a unique image for the "Observe my Kubernetes
infrastructure" card - I uploaded the image (`kubernetes.png` and
`kubernetes-dark.png`), but did not replace it. I tried too initially,
but kept getting errors when adding it to the`UseCase` map, so left it
for now as the page now does not show a unique image. That being said I
am more than happy to replace it - I just might need some direction 😜,
or I can create a future task for that. Whatever you think is best.

packages/kbn-guided-onboarding/src/components/landing_page/use_case_card.tsx

@@ -101,11 +101,14 @@ export const UseCaseCard = ({
         <EuiImage
           src={getImageUrl(constants[useCase].imageUrlPrefix)}
           alt={constants[useCase].logAltText}
+          size={200}
+          margin="s"
         />
       }
       title={titleElement}
       description={description}
       footer={footer}
+      paddingSize="l"
       betaBadgeProps={{
         label: constants[useCase].betaBadgeLabel,
       }}