chore: add warmup tests for defer

[ysmolski]

Also I have included countries subgraph into the demo stack

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Router-nonroot image scan passed

✅ No security vulnerabilities found in image:

ghcr.io/wundergraph/cosmo/router:sha-638a61716d79a76a92300d9b26f48d59199afc6e-nonroot

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 40.73%. Comparing base (7367168) to head (a9c0eaf).
⚠️ Report is 2 commits behind head on feat/eng-7770-add-defer-support.

Additional details and impacted files

@@                         Coverage Diff                         @@
##           feat/eng-7770-add-defer-support    #3001      +/-   ##
===================================================================
+ Coverage                            40.25%   40.73%   +0.48%     
===================================================================
  Files                                  244      244              
  Lines                                29600    29600              
===================================================================
+ Hits                                 11914    12058     +144     
+ Misses                               16326    16196     -130     
+ Partials                              1360     1346      -14     

see 16 files with indirect coverage changes

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