Treat each exported service as a "discovery chain" and replicate one
synthetic CheckServiceNode for each chain and remote mesh gateway.
The health will be a flattened generated check of the checks for that
mesh gateway node.
By changing to use WatchCtx we will actually block for changes to the peering list. WatchCh creates a goroutine to collect errors from WatchCtx and returns immediately.
The existing behavior wouldn't result in a tight loop because of the rate limiting in the surrounding function, but it would still lead to more work than is necessary.