[Stack Monitoring UI] Use the official KibanaThemeProvider

[weltenwort]

📓 Summary

In order to support the new theming mechanism of EUI we need to include the recently added <KibanaThemeProvider> in the app component hierarchy.

part of #118866

✔️ Acceptance criteria

• The function that mounts the react hierarchy of the monitoring app wraps the hierarchy into a <KibanaThemeProvider> with props from the core theme$ argument.

💡 Implementation hints

• [meta] Adapt all existing applications to use the new KibanaThemeProvider #118866 provides a bit of example code

[elasticmachine]

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

[jasonrhodes]

Do we know if this has an explicit deadline when it needs to be done?

[weltenwort]

The meta issue indicates that EUI will rely on this provider to be present by 8.1 FF.