Improve repeated server testing UX

[Victor239]

Current UX is that after completing your first speed test and clicking "New test", you're then booted to the home screen which then is "Selecting servers" for a few seconds again, and then it picks a new server for you.

A few changes could be made here:

• It doesn't need to be "Selecting servers" for the second (or third, or fourth, etc) time in the same session. Remember what servers exist for at least the duration the app is open (but ideally it'd only be required to check again after say 24 hours).
• Remember the server that was selected for the first test. For the second test it automatically picked a server for me which was several countries away when I had already tested with a server in my own country.
• Show a table for the last few tests made (date/time column, server selected, then the speed values).