fix: restore REST all mod versions response contents

[mircearoata]

Since the ent refactor, the dependencies list was null, and a lot of blank fields were returned, because a GraphQL response type was used, but was not filled in.

Also adds a Link field to the targets in the response, like the Link in the Version type on the GraphQL API, such that ficsit-resolver doesn't need to construct the downloads links based on the version ID and target name.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 55 lines in your changes missing coverage. Please review.

Project coverage is 19.83%. Comparing base (d13695d) to head (8a18a0a).
Report is 1 commits behind head on staging.

Files	Patch %	Lines
generated/conv/version.go	0.00%	48 Missing ⚠️
conversion/ent_to_rest.go	0.00%	4 Missing ⚠️
nodes/mod.go	0.00%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           staging      #82      +/-   ##
===========================================
- Coverage    19.84%   19.83%   -0.02%     
===========================================
  Files          229      230       +1     
  Lines        57102    57154      +52     
===========================================
  Hits         11334    11334              
- Misses       43303    43355      +52     
  Partials      2465     2465              

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