refactor(nodebuilder): Allow custom networks to work over already-initialised store

[renaynay]

After conversation with @jbowen93 , we decided to allow using custom networks over an already-initialised node store.

The issue this was originally attempting to prevent is accidental corruption of chain data in the case that a user accidentally leaves their environment variable set up and connects to another network over an old node store.

This issue is actually currently prevented thanks to #1073 extending the node store name with the network name.

[codecov-commenter]

Codecov Report

Merging #1270 (3caad63) into main (0e48f9a) will decrease coverage by 0.01%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #1270      +/-   ##
==========================================
- Coverage   56.17%   56.15%   -0.02%     
==========================================
  Files         160      160              
  Lines        9939     9935       -4     
==========================================
- Hits         5583     5579       -4     
  Misses       3802     3802              
  Partials      554      554              

Impacted Files	Coverage Δ
nodebuilder/init.go	65.71% <ø> (+2.20%)	⬆️
header/core/listener.go	52.83% <0.00%> (-5.67%)	⬇️
share/ipld/get.go	92.59% <0.00%> (ø)

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