[Flow Framework] Add containsModels param to handle custom/empty template

[ohltyler]

Description

Add containsModels param to handle custom/empty template. We don't want to search for models for this template, which does not require one.

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[ohltyler]

Result from running tests on a template with models, and one without:

  Creating Workflows Using Various Methods
    - Import workflow with valid configuration
    - Attempt to import workflow with invalid configuration
    - Create workflow using semantic search template
    - Create workflow from hybrid search template
    ✓ Create workflow from multimodal template (229902ms)
    ✓ Create workflow from custom template (154730ms)


  2 passing (7m)
  4 pending


  (Results)

  ┌────────────────────────────────────────────────────────────────────────────────────────────────┐
  │ Tests:        6                                                                                │
  │ Passing:      2                                                                                │
  │ Failing:      0                                                                                │
  │ Pending:      4                                                                                │
  │ Skipped:      0                                                                                │
  │ Screenshots:  0                                                                                │
  │ Video:        true                                                                             │
  │ Duration:     6 minutes, 44 seconds                                                            │
  │ Spec Ran:     plugins/dashboards-flow-framework/create_workflow_spec.js                        │
  └────────────────────────────────────────────────────────────────────────────────────────────────┘


  (Video)

  -  Started processing:  Compressing to 32 CRF                                                     
    Compression progress:  71%
  -  Finished processing: /Users/ohltyler/workspace/opensearch/3.0/opensearch-dashboa   (21 seconds)
                          rds-functional-test/cypress/videos/plugins/dashboards-flow-               
                          framework/create_workflow_spec.js.mp4                                     

    Compression progress:  100%

====================================================================================================

  (Run Finished)


       Spec                                              Tests  Passing  Failing  Pending  Skipped  
  ┌────────────────────────────────────────────────────────────────────────────────────────────────┐
  │ ✔  plugins/dashboards-flow-framework/c      06:44        6        2        -        4        - │
  │    reate_workflow_spec.js                                                                      │
  └────────────────────────────────────────────────────────────────────────────────────────────────┘
    ✔  All specs passed!                        06:44        6        2        -        4        -