Use Observability Page Template from Observability Shared in Infra

[CoenWarmer]

Resolves #154777

📝 Summary

As part of #154735 a Observability Shared app was created, which exports the Observability Page Template.

This PR updates the Infra app to use the Observability Page Template from Observability Shared.

More details about the change in the PR linked above. Summarized, this change comes down to:

✅ Checklist

• All links and navigation should behave exactly as before.

[apmmachine]

🤖 GitHub comments

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Just comment with:

• /oblt-deploy : Deploy a Kibana instance using the Observability test environments.
• run elasticsearch-ci/docs : Re-trigger the docs validation. (use unformatted text in the comment!)

[elasticmachine]

Pinging @elastic/infra-monitoring-ui (Team:Infra Monitoring UI)

[tonyghiani]

LGTM, thanks for applying the change!

[kibana-ci]

💚 Build Succeeded

• Buildkite Build
• Commit: a7d92bd

Metrics [docs]

Async chunks

Total size of all lazy-loaded chunks that will be downloaded as the user navigates the app

id	before	after	diff
infra	2.0MB	2.0MB	+24.0B

Page load bundle

Size of the bundles that are downloaded on every page load. Target size is below 100kb

id	before	after	diff
infra	90.0KB	90.0KB	+6.0B

Unknown metric groups

ESLint disabled line counts

id	before	after	diff
securitySolution	432	435	+3

Total ESLint disabled count

id	before	after	diff
securitySolution	512	515	+3

History

• 💔 Build #120203 failed 391f8d643aaccd2dbf5744691ceedefa90967d69
• 💚 Build #119215 succeeded ef15de5
• 💔 Build #119194 failed 4d7f3e6

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@elasticmachine merge upstream