feat: remember node counts when creating new networks

[jamaljsr]

Description

When repeatedly creating new networks for testing, I often want to use the same count of nodes that I used on the previously created network. It's a minor annoyance to have to change the counts each time. This PR just saves the node counts when you create a new network and uses those values the next time you go to the New Network screen.

Steps to Test

1. Click New Network
2. Change the node counts to different values
3. Click Create Network
4. Delete the network
5. Restart Polar
6. Click New Network
7. Confirm the initial node counts are what you previously set

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (c25b429) to head (e7f8e3d).

Additional details and impacted files

@@            Coverage Diff            @@
##            master      #895   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files          140       140           
  Lines         4581      4582    +1     
  Branches       852       887   +35     
=========================================
+ Hits          4581      4582    +1     

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