Add an initial Networks search box to the All Networks dashboard
s/blogs/search-networks/ for action ID
Update the action URL for the site list

Uses our display=network to display the correct table. Also modifies the action to 'all-networks', which we may want to revisit again at some point.
Display search results text at the top of the All Networks page
Display the network name in the networks list table
Update WordPress tracking commit
Indicate network ID, name, and domain as sortable columns