[CI] fix coverage_report in daily test

[EmmonsCurse]

Motivation

Enable Codecov to upload coverage reports both for PRs and for post-merge runs.

Modifications

• Downloaded the full coverage report (python_coverage_all.xml) instead of generating a diff when not triggered by a PR.
• Configured Codecov uploader with appropriate flags (GPU) and disabled CI fail-on-error to avoid blocking post-merge runs.

Usage or Command

N/A

Accuracy Tests

N/A

Checklist

• Add at least a tag in the PR title.
  • Tag list: [[FDConfig],[APIServer],[Engine], [Scheduler], [PD Disaggregation], [Executor], [Graph Optimization], [Speculative Decoding], [RL], [Models], [Quantization], [Loader], [OP], [KVCache], [DataProcessor], [BugFix], [Docs], [CI], [Optimization], [Feature], [Benchmark], [Others], [XPU], [HPU], [GCU], [DCU], [Iluvatar], [Metax]]
  • You can add new tags based on the PR content, but the semantics must be clear.
• Format your code, run pre-commit before commit.
• Add unit tests. Please write the reason in this PR if no unit tests.
• Provide accuracy results.
• If the current PR is submitting to the release branch, make sure the PR has been submitted to the develop branch, then cherry-pick it to the release branch with the [Cherry-Pick] PR tag.

[paddle-bot]

Thanks for your contribution!

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
⚠️ Please upload report for BASE (develop@c06cfe2). Learn more about missing BASE report.

Additional details and impacted files

@@            Coverage Diff             @@
##             develop    #5175   +/-   ##
==========================================
  Coverage           ?   57.66%           
==========================================
  Files              ?      317           
  Lines              ?    38445           
  Branches           ?     5762           
==========================================
  Hits               ?    22171           
  Misses             ?    14499           
  Partials           ?     1775           

Flag	Coverage Δ
GPU	57.66% <ø> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.