FE: Adjust button states w/ r/o mode

[Haarolean]

There is a cluster read-only mode. Not all the altering actions on the frontend are unavailable when a cluster is r/o.
Fix this, perhaps add a check on button/other component level.

Related:

• In read-only mode, it remains possible to edit the broker's configuration provectus/kafka-ui#4374

[spartanns]

Hi! I'd like to try this one out.