v2 emit

[jerbly]

Uses the --v2 switch to emit v2 ForgeRegistry to OTLP.

• Initial cut, make it work.
• Refactor duplicated code.
• v2 specific tests.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.6%. Comparing base (becc36e) to head (faf6328).

Additional details and impacted files

@@           Coverage Diff           @@
##            main   #1019     +/-   ##
=======================================
+ Coverage   78.5%   78.6%   +0.1%     
=======================================
  Files         82      82             
  Lines       6564    6606     +42     
=======================================
+ Hits        5157    5198     +41     
- Misses      1407    1408      +1     

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