We'd like to observe individual last signed height for validators via Prometheus by requesting a tendermint_consensus_last_signed_height metric with the following labels:

• address (example: "E33032D801DA4D124FBF696DEF7832E415EA74EE")
• operator (example: "cosmosvaloper1lc4jjw8zveuuj3njhy70zl23vgmpds2xg830hn")
• chain_id (example: cosmoshub-2)

As some might object to the cardinality of this (100+ validators on cosmoshub-2), a config option to enable this could be beneficial as well. Request is related to per-validator voting power in #3083, so a common toggle for per-validator observability would be suitable.

Thanks for your consideration. :-)