chore: consolidate constants for workspace and ragengine controller

[bangqipropel]

Reason for Change:
consolidate constants for workspace and ragengine controller

Requirements

• added unit tests and e2e tests (if applicable).

Issue Fixed:

Notes for Reviewers:

[codecov]

Codecov Report

Attention: Patch coverage is 13.69863% with 63 lines in your changes missing coverage. Please review.

Project coverage is 54.49%. Comparing base (5c30038) to head (85f57e0).
Report is 30 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/controllers/workspace_controller.go	1.66%	52 Missing and 7 partials ⚠️
api/v1alpha1/workspace_validation.go	0.00%	2 Missing ⚠️
api/v1alpha1/ragengine_validation.go	0.00%	1 Missing ⚠️
pkg/inference/preset-inferences.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #631      +/-   ##
==========================================
- Coverage   58.18%   54.49%   -3.69%     
==========================================
  Files          30       34       +4     
  Lines        2987     3257     +270     
==========================================
+ Hits         1738     1775      +37     
- Misses       1149     1376     +227     
- Partials      100      106       +6     

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[zhuangqh]

I don't think it's necessary to replace the log key with a constant variable. you can find literal object name keys all over the kubernetes code. https://github.com/search?q=repo%3Akubernetes%2Fkubernetes+KObj&type=code&p=1

[Fei-Guo]

Yes, for logs, just use KObj and remove redundant information.