A new health check function _timescaledb_internal.health() returns the
health and status of the database instance, including any configured
data nodes (in case the instance is an access node).
Since the function returns also the health of the data nodes, it tries
hard to avoid throwing errors. An error will fail the whole function
and therefore not return any node statuses, although some of the nodes
might be healthy.
The health check on the data nodes is a recursive (remote) call to the
same function on those nodes. Unfortunately, the check will fail with
an error if a connection cannot be established to a node (or an error
occurs on the connection), which means the whole function call will
fail. This will be addressed in a future change by returning the error
in the function result instead.
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