Chore: refactor suspend step and add op.#Suspend

[FogDong]

Description of your changes

This PR refactor suspend step, add new phase suspending and add op.#Suspend .

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.

How has this code been tested

Special notes for your reviewer

[codecov]

Codecov Report

Base: 67.97% // Head: 68.24% // Increases project coverage by +0.27% 🎉

Coverage data is based on head (dd9e3a4) compared to base (edc7849).
Patch coverage: 56.41% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #138      +/-   ##
==========================================
+ Coverage   67.97%   68.24%   +0.27%     
==========================================
  Files          48       47       -1     
  Lines        4334     4283      -51     
==========================================
- Hits         2946     2923      -23     
+ Misses       1022      996      -26     
+ Partials      366      364       -2     

Flag	Coverage Δ
e2etests	25.43% <7.69%> (+0.36%)	⬆️
unit-test	65.13% <52.56%> (+0.21%)	⬆️

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

Impacted Files	Coverage Δ
api/v1alpha1/types.go	11.11% <ø> (ø)
pkg/cue/model/sets/operation.go	74.38% <ø> (ø)
pkg/tasks/builtin/step_group.go	62.13% <0.00%> (-6.69%)	⬇️
pkg/tasks/custom/task.go	70.14% <0.00%> (-1.28%)	⬇️
pkg/tasks/discover.go	93.33% <ø> (-0.42%)	⬇️
pkg/types/types.go	33.33% <ø> (ø)
pkg/executor/workflow.go	81.33% <69.69%> (-0.06%)	⬇️
pkg/providers/workspace/workspace.go	81.39% <74.07%> (-3.61%)	⬇️
pkg/generator/generator.go	68.54% <100.00%> (ø)

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