chore: Refactor to implement model plugin - part 3

[Fei-Guo]

This change activates all model plugins.

• Remove all hard coded model name in workspace_controller.go by using the plugin modelregister.
• Fix related UTs
• Change the model interface for better abstraction
• Change to use Deployment for llama2-7b models.

[codecov]

Codecov Report

Attention: 14 lines in your changes are missing coverage. Please review.

Comparison is base (2d0c593) 77.05% compared to head (31c7472) 77.89%.

Files	Patch %	Lines
pkg/controllers/workspace_controller.go	67.74%	6 Missing and 4 partials ⚠️
pkg/inference/preset-inferences.go	85.71%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #189      +/-   ##
==========================================
+ Coverage   77.05%   77.89%   +0.84%     
==========================================
  Files           9        9              
  Lines        1142     1095      -47     
==========================================
- Hits          880      853      -27     
+ Misses        226      208      -18     
+ Partials       36       34       -2     

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