Chore: Fetch workflowstepdefinitions CRD from KubeVela repository

[vaibhav0096]

Description of your changes

Fixes #

I have:

• Read and followed KubeVela's contribution process.
• Related Docs updated properly. In a new feature or configuration option, an update to the documentation is necessary.
• Run make reviewable to ensure this PR is ready for review.
• Added backport release-x.y labels to auto-backport this PR if necessary.

---

Summary by cubic

Fetch workflowstepdefinitions CRD directly from the KubeVela repo during sync-crds to prevent drift, with version control via KUBEVELA_VERSION. Also synced the chart CRD to match upstream.

• Refactors
  • Added KUBEVELA_VERSION (default: master) and KUBEVELA_RAW_URL in const.mk.
  • Updated sync-crds to download core.oam.dev_workflowstepdefinitions.yaml from kubevela/charts/vela-core/crds via GitHub raw.
  • Aligned charts/vela-workflow CRD with upstream (newline at EOF).

^{Written for commit 5dfea1b. Summary will update automatically on new commits.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 70.19%. Comparing base (d7db9c4) to head (462eb23).
⚠️ Report is 7 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #221      +/-   ##
==========================================
+ Coverage   62.49%   70.19%   +7.70%     
==========================================
  Files          62       62              
  Lines        4415     5009     +594     
==========================================
+ Hits         2759     3516     +757     
+ Misses       1324     1142     -182     
- Partials      332      351      +19     

Flag	Coverage Δ
e2etests	21.39% <ø> (?)
unit-test	64.22% <ø> (+1.73%)	⬆️

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[cubic-dev-ai]

No issues found across 3 files