Rename `bridge_status` to `bridge_network_status_entry`

For our relays we have the network_status table for a network status document and network_status_entry for individual entries, which makes sense. However, for bridges we currently have bridge_network_status for the status document (which is fine) but then bridge_status for the particular entry. However, that is confusing things easily with the network_status part which is pointing to a whole document and not a single entry like the current bridge_status is doing.

To make things easier, let's rename bridge_status to bridge_network_status_entry instead.