Add basic tests of registry compute complexity for protos, openapi, and discovery formats

[timburks]

This verifies that the computation runs and computes something for the three formats.

testdata is identical to the testdata in the vocabulary package, these could be merged and pulled up a level if desired.

[codecov]

Codecov Report

Merging #1116 (d9b1c65) into main (df7c3b4) will increase coverage by 0.76%.
The diff coverage is 100.00%.

❗ Current head d9b1c65 differs from pull request most recent head 407d3e4. Consider uploading reports for the commit 407d3e4 to get more accurate results

@@            Coverage Diff             @@
##             main    #1116      +/-   ##
==========================================
+ Coverage   69.13%   69.90%   +0.76%     
==========================================
  Files         145      145              
  Lines       12017    12022       +5     
==========================================
+ Hits         8308     8404      +96     
+ Misses       2985     2890      -95     
- Partials      724      728       +4     

Impacted Files	Coverage Δ
cmd/registry/tasks/tasks.go	100.00% <100.00%> (+5.26%)	⬆️

... and 4 files with indirect coverage changes

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more