[componentstatus] Consider removing timestamp from Event

[TylerHelmuth]

          Timestamp seem to be use-less, because it is always "now", which means consumers (watchers) can also read if they need it.

Originally posted by @bogdandrutu in #10730 (comment)

[mwear]

I believe that we should keep the timestamp as the observed time is not the same time as the observation. Since status watchers are dispatched in sequence, any status watcher that does a non-trivial amount of work, or something that could block (like writing to an event to a channel) could delay the observed time for subsequent watchers. This would be especially problematic if the delay was variable between invocations. Currently the timestamp is used by the health check extension for time calculations.