ci: use codecov token when uploading reports

[pichlermarc]

Description

See open-telemetry/opentelemetry-js#5053 in the core repo.

The same problem exists here - commits on main are not created in codecov because we're missing the token, which means that the reports on the PRs are hundreds of commits behind. (see recent run on main https://github.com/open-telemetry/opentelemetry-js-contrib/actions/runs/11241062146/job/31251798449#step:11:80)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.74%. Comparing base (dfb2dff) to head (9dd142e).
Report is 256 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2468      +/-   ##
==========================================
- Coverage   90.97%   90.74%   -0.24%     
==========================================
  Files         146      156      +10     
  Lines        7492     7723     +231     
  Branches     1502     1588      +86     
==========================================
+ Hits         6816     7008     +192     
- Misses        676      715      +39     

see 76 files with indirect coverage changes