Adjust Kuma reports on preview, preprod and mainnet versions of GovTool

[bosko-m]

We've recently experienced issues with preview not being operational meaning drep directory and governance actions pages would not load with just loading spinners being displayed infinitely.
At that moments Kuma reports showed all systems operational on preview.gov.tools.
Therefore, Kuma status report should be updated so it can better reflect this scenario and transparently shows that system is not fully operational.
@spannercode rightfully pointed out: "Since the page is rendered client side using react, uptime status check for frontend pages seems insufficient as it only checks for 200 response"