Revert Datadog testagent version from 1.18.0 to 1.12.0

[sarahchen6]

What does this PR do?
This PR changes the Datadog testagent version from 1.18.0 back to 1.12.0 in the docker-compose.yml and .circleci/config.yml.

Motivation:
Testagent v1.18.0 causes local tracing parsing errors, such as: ERROR -- datadog: [datadog] (/app/lib/datadog/tracing/transport/http/client.rb:42:in 'rescue in send_request') Internal error during Datadog::Tracing::Transport::HTTP::Client request. Cause: JSON::ParserError unexpected token at '{"rate_by_service": {"service:,e' Location: /usr/local/bundle/gems/json-2.7.5/lib/json/common.rb:220:in 'parse'. No particular functionality of v1.18.0 was needed, and reverting the version to 1.12.0 fixes these errors.

Change log entry
No change log entry needed.

Additional Notes:
N/A

How to test the change?
To test this change, run docker compose run --rm -it tracer-<version number> bash -c "rm *lock && bundle install && bundle exec rake spec:main" locally. All tests should pass, whereas previously, you would see many tracing errors.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.73%. Comparing base (51446c7) to head (13c845f).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4060      +/-   ##
==========================================
+ Coverage   97.72%   97.73%   +0.01%     
==========================================
  Files        1338     1338              
  Lines       80249    80249              
  Branches     4016     4016              
==========================================
+ Hits        78422    78431       +9     
+ Misses       1827     1818       -9     

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[pr-commenter]

Benchmarks

Benchmark execution time: 2024-11-01 20:07:37

Comparing candidate commit 13c845f in PR branch sarahchen6/revert-testagent-version with baseline commit 51446c7 in branch master.

Found 0 performance improvements and 0 performance regressions! Performance is the same for 29 metrics, 2 unstable metrics.

[Strech]

All right!

[ivoanjo]

I'm guessing this is the "stop the bleeding PR" which makes sense; but we should also make sure to ping the folks that maintain the test agent to let them know that 1.18.0 appears broken, as permanently staying on an old version doesn't seem great.

[sarahchen6]

I'm guessing this is the "stop the bleeding PR" which makes sense; but we should also make sure to ping the folks that maintain the test agent to let them know that 1.18.0 appears broken, as permanently staying on an old version doesn't seem great.

I agree. Will do!