refact: use the Load function uniformely in all the yaml loaders

[dido18]

Motivation

The CLI has 3 YAML loaders for loading app.yaml, bricks-list.yaml and model-lists.yaml but the API are not uniform.

These are the current APIS for each loader:

• modelindex.GenerateModelsIndexFromFile(dir *paths.Path) (*ModelsIndex, error)
• bricksindex.GenerateBricksIndexFromFile(dir *paths.Path) (*BricksIndex, error)
• app.Load(appPath string) (ArduinoApp, error)

Change description

Change the method to load the file as follows:

• modelsindex.Load(dir *path.Path)(*ModelsIndex, error)
• bricksindex.Load(dir *paths.Path) (*BricksIndex, error)
• app.Load(apppath *paths.Path)(ArduinoApp, error)

Additional Notes

Reviewer checklist

• PR addresses a single concern.
• PR title and description are properly filled.
• Changes will be merged in main.
• Changes are covered by tests.
• Logging is meaningful in case of troubleshooting.