fix(ci): wire GitLab CI to publish the system-tests image

[MilanGarnier]

Stacked on #4065 — needs the GH Actions workflow merged to master first
(workflow_dispatch resolves the workflow by filename against the
default branch, regardless of dispatch ref).

Summary

• Adds a check open pr for system tests job that gates on an open
  GitHub PR before anything is uploaded to S3, addressing:
  fix(ci): publish system-tests image via S3 + GH Actions dispatch #4065 (comment)
• Splits the old single job into upload + dispatch, both gated on that
  check via a dotenv artifact.

Test plan

• Merge fix(ci): publish system-tests image via S3 + GH Actions dispatch #4065 to master first
• Rebase this branch onto master, retarget base to master
• Push a throwaway branch with an open PR, confirm S3 upload +
  dispatch + image push succeed end to end
• Push a branch with no open PR, confirm S3 upload is skipped

[datadog-datadog-prod-us1-2]

 

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⚠️ Warnings

🚦 142 Pipeline jobs failed

DataDog/apm-reliability/dd-trace-php | PHP Language Tests: [8.0]     

🧪 3 Tests failed

ext/curl/tests/curl_basic_008.phpt (Test curl_error() & curl_errno() function with problematic host) from PHP.ext.curl.tests  

001+ DNS resolution failurestring(0) ""
002+ int(0)
001- %s resolve%s
002- int(6)

ext/curl/tests/curl_error_basic.phpt (curl_error() function - basic test for curl_error using a fake url) from PHP.ext.curl.tests  

== Testing curl_error with a fake URL ==
002+ string(0) ""
002- string(%d) "%sfakeURL%S"

View all failed tests

DataDog/apm-reliability/dd-trace-php | PHP Language Tests: [8.1]     

🧪 1 Test failed

ext/curl/tests/curl_error_basic.phpt (curl_error() function - basic test for curl_error using a fake url) from php.ext.curl.tests  

== Testing curl_error with a fake URL ==
002+ string(0) ""
002- string(%d) "%sfakeURL%S"

DataDog/apm-reliability/dd-trace-php | PHP Language Tests: [8.5]     

🧪 2 Tests failed

ext/curl/tests/curl_basic_008.phpt (Test curl_error() & curl_errno() function with problematic host) from php.ext.curl.tests  

001- %s resolve%s
002- int(6)
001+ DNS resolution failurestring(0) ""
002+ int(0)

sapi/cgi/tests/apache_request_headers.phpt (apache_request_headers() stack overflow.) from php.sapi.cgi.tests  

--
     
     Array
     (
006+     [Proxy] => http://127.0.0.1:15002
     )
     Array
     (
         [X-Test] => AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
011+     [Proxy] => http://127.0.0.1:15002
...

View all 142 failed jobs.

ℹ️ Info

No other issues found (see more)

❄️ No new flaky tests detected

🔄 Datadog auto-retried 1 job - 0 passed on retry

🎯 Code Coverage (details)
• Patch Coverage: 100.00%
• Overall Coverage: 87.72% (+0.05%)

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