status: Expose datetime of most recent block

[ptrus]

Resloves https://app.clickup.com/t/866af85d2

Testing (locally):

curl "localhost:8008/v1/"
{"latest_block":8049056,"latest_block_time":"2022-04-11T13:12:48+02:00","latest_update":"2023-06-25T09:20:13+02:00"}


curl "localhost:8008/v1/emerald/status"
{"active_nodes":0,"latest_block":1004425,"latest_block_time":"2022-04-11T17:04:34+02:00","latest_update":"2023-06-25T09:18:49+02:00"}

[aefhm]

Happy weekend LGTM, but defer to the other gents.

[pro-wh]

lg here too

[mitjat]

Thank you, LGTM also!
Bummer that we "have to" make a separate query (instead of using a JOIN) because of the consensus/runtime distinction.

[mitjat]

Since the change is pretty small and there are no reviewer suggestions, I'll go against convention and merge this PR in. This way, it can make it into the release I'm hoping to cut in the next few hours.